I have a 4 burner w/griddle Viking range. I am upgrading to a six burner for new house. I will definitely use all much of the time. I cook from scratch 2-3 meals a day. I have 9 children still living at home.
Some of the things I cook.... all homemade stocks for soups, stews, casseroles. Pasta sauces, vegetables, quiches, tarts, all types of desserts, jams, jellies, and chutney's just to name a few. Actually there are too many to mention.
I do love to cook and am so thrilled to be getting six burners.

acountryfarm, My compliments to you. Are you sure six burners are enough?

We have a six burner cooktop and thus far, it's true, we rarely need five or six of the burners at once. However, at present we only use the rear burners (we've two small children so it's merely a safety issue for us). That being said, we still do regularly use (as I wrote) three - four of them, and I can only imagine we'll use more as our children allow.

Oh yeah, in our previous kitchen we had a 45" four burner / griddle cooktop and can I tell you how much we loved that width! Our six burner is only 36" and we really miss those missing inches. Granted, the old cooktop was electric and this one is gas (we'd never, ever go back!). And with that four burner (electric) cooktop there were times we needed a fifth or sixth burner and it was tough luck for us!

I guess it really depends on the way you cook.

I've been living with 4 all along and have done just fine. However, in the process of this remodel, we opted to go for a 36" six burner (will have the griddle in place most of the time, so really 4 burners and a griddle) because we are making such an investment in the kitchen and would hate to then want to upgrade in the future and have to undo a lot of what we've done.

I do think we will often use three of the burners and the griddle - we have a cheapie electric countertop griddle now and use it all the time.

We have 6 burners and a griddle. I don't think we've ever used 6 burners at once but we often have very large stockpots and frying pans on the stove and the extra space comes in handy. I couldn't have 3 of these on our old 4-burner stove at once and have them centered over burners. I love having free cold burners for pots coming off the hot burners that need to cool off or for placing items coming out of the oven. DH will often come cook some of his own concoctions while I'm cooking. He has his 2 burner end and I have my 4 burner end and plenty of elbow space. Also, I can take a dish out of the fridge and set it down on a cold burner to warm up over the preheating oven before popping it in (I've had a couple of pyrex dishes explode when going straight from fridge to hot oven.) AND, since we use a lot of cast iron we can wash a pan and dry it on the burner while other items are cooking.

So even though I'm not cooking 6 items on the stove at once, I find the 6 burners very useful. I don't feel as though it was a wasted expense.

For day-to-day use, I don't really need 6 burners, but there had been a number of times over the years when I'd wished for at least one more burner (cooking for a crowd--holidays, special get-togethers, trying out those recipes that seem to involve every pan one owns...), and/or wanting more space between the burners I did have (when I make chicken soup, I like to make several large stockpots of it at one time).

I will be getting 6 burners. I think 5 would have been plenty, but my DH wants the professional looking rangetop instead of cooktop. Tonight, I did have pasta sauce on one burner, wheat pasta on another, regular pasta on one and tortellini on a 4th. I would have liked two more burners just to open up space!

On my new stove top, i will have a griddle pan (accessory) that covers two burners. I will probably keep it on there most of the time and just move it when I think I need a 5th burner.

Also, I kind of chose the stovetop to be in proportion with the rest of the kitchen. It really could use a 48" stove, but I just didn't want that much--or to spend that much, but the kitchen is big enough that just four burners would probably have seemed a bit small.

I thought my 6-burner Bluestar was more hobs than I required, but I have to say that after a week of using it, I am very glad I got the extra burners, pretty much for the reasons zelmar cited. Our family is 7 people and my big cast iron fry pans take up a lot of space. Also, on the Bluestar, I wanted two equally-powerful burners in the middle, for when I would want to span two burners with a griddle or roasting pan.

The big drawback of the 36" ranges is the length of time the oven takes to preheat (half hour to 40 min).

At my previous home I had a 6 burner Jenn-Air. I don't think I ever really used all 6 burners at one time. So for this home, I bought a 36" Bluestar range with 4 burners and a griddle. I do, however, have an abundance of ovens. Besides the large 36" gas oven on the Bluestar, I have a 30" electric/convection oven, a combination microwave/convection oven that I use to bake small items, plus a warming drawer. This combination has worked extremely well for us.

I decided that if it turned out that I really did need more than 4 burners, I would buy a separate induction unit that I could set on the counter as needed. I haven't needed to do that yet.

My husband and I are empty nesters, but our kids and their friends come often, plus we love to entertain.

I don't often use all 6 at once, but I often have all 6 covered. Let me explain. I might have 3-4 in use, but then have 2 covered with things that just came out of the oven, and 1 covered with something that is about ready to be turned on (or was just turned off). I don't like to put anything hot anywhere but the cooktop. I infrequently use all 6, maybe when having a party or cooking for a holiday. I would never get less than 6. If I was doing another kitchen and had the money and space I might even do 8 (which I what DH wanted but I thought was overkill).

I graduated from a cooktop with 2 working burners to 6-burner Wolf range top. I find myself using the front 3 burners for cooking, and using the back three burners for sliding hot pots from the front backward to cool. Up to now, I don't think I've used more than 2 burners at the same time (after 10 years with the previous cooktop, I got used to cooking EVERYTHING on 2 burners). BUT, I can see myself in the near future using the back burners for pots needing a long, slow simmer (soups, pasta sauces, and homemade mincemeat come to mind) while I'm cooking dishes for more immediate use on the front burners.

I currently have a regular 30 inch gas range but going for 36" for the remodel. My reasons are the same as Zelmar's with the most important being enough room for three large items. I did find that 30" DCS range with its unique spacing would also work for three large pots/pans but it was the only one and I didn't want to have it as the only option. We are still far away from being done so I am still to see how I like the new size. But if there are layout limitations and 30" fits better, there is always an option of a portable induction burner when you need one as Nuccia said or just planning the meals accordingly.

I have 4 burner only because I couldnt find something smaller.

cooking usage percentage
1 burner - 90%
2 burners - 9%
3 burners - 1%
4 burners - never. I get too hot standing near so much heat from the blue star :)

If I had to do this over, i would choose a two burner set up but in two range tops. ie two single-burner rangetops if there is such a thing. Imagine a big island with two cooking areas each with a single burner.

I recently read somewhere that 1-2 people only need a two burner cooktop, a 24" oven, and a microwave. But the pro style hefty (36" & 48") ranges & rangetops are very seductive.

You would think that if there are a moderate number of two-people households and space-constrained urban apartment dwellers, there would be more good 24 inch wall ovens and 2-or 4-burner cooktops. If you want a 4 burner rangetop with open burners you have only one choice: Blue Star. It seems that more and more ranges are going to the closed burners. Wolf offers quasi open burner but in the rangetop, they only offer 6, not 4. (curiously if you go for the range there are more 30 inch options but then you have to get the 30 inch oven!)

A 30 inch oven looks huge to me. Even my current 27 inch oven rarely gets used. Why aren't there more 24 inch ovens? Why are the open burners going away?

I am sure you can do it on less. When we were doing a large reno on current home I had a temporary kitchen.
Two large roasters, crock pot, & 2 burner counter top hot plate. I cooked for DH & 10 children for 6 months this way. We ate well. I also did thanksgiving dinner (including 6 pies) for 18 with the same set up. While I would never want to do it again, I could. It definitely makes me appreciate my wonderful kitchen.

Our first house had 6 and a griddle. This house has one range with 6 big burners, a griddle, and another cooktop with an additional 4 low BTU burners, so 10. No, I don't use all 6 large burners all the time. However, I often use 4 for active cooking and one for simmering stock or marinara. I also do significant canning (except deer and armadillos destroyed this year's garden, drat!). I use many large stockpots at once and then divide and freeze stock and sauce. One house had a 5-burner cooktop and it did not provide enough room. I use my small pots on the little cooktop, but, honestly, I don't use the small pots very often. We have 4 kids, 2 sons-in-law, one grandbaby, another on the way. It's wonderful to have family reunions and fundraisers and not worry about having enough room. (I have cooked on yachts and in teeny Parisian apartments, so I know that marvelous food can be produced under many kinds of conditions, but I love not feeling claustrophobic and not worrying where to put down a hot pot!) It's more difficult for me to lift heavy pots and pans than it once was, so I really value being able to slide heavy, hot pans around.

I've always had 4 until now. I love my 6. For a chinese-style dinner: a wok on one, a large frying pan on another; rice on another; pan and steamer on another; - there's enough room now that the wok doesn't overlap. Previously, on a 4 burner, I could only use the wok and one other burner, because it overhung the others.
My typical English Sunday dinner: A roast in the oven. A pan to parboil the potatoes, prior to roasting; A pan of giblet stock, ready to make gravy; a pan of dressing; a pan with steamer for vegetables; another pan for vegetables.

And, if I'm lucky, there'll be some attempt at dessert in there too.

The biggest benefit is simply being able to move pans around more conveniently.

Reading some of these answers, I have to say that having a bigger range is a pretty expensive way to replace trivets or hot pads - which is why we have tile countertops, but that's another thread...
Family of five: mom, dad, 2 sons, grandmother who doesn't like anything I cook except my brined roasted chickens. After about 1 year of use, this is roughly our usage:

We love our 6-burner Wolf and use the two front corners just about every breakfast and dinner, and the front three or combo of 4 a few times a week, and five a few times a month. I think we've only used all 6 twice - something like this: boiling chicken, simmering enchilada sauce, cooking Spanish rice, mashing refried beans, heating up tortillas (or frying queso), steaming veggie du jour.