I think it depends what you're thinking of starting. I've got peppers, tomatoes & squash (that I goofed and started too early I'm afraid) inside. I've got some under lights and some in the south window.

For my cool weather crops, (lettuce, broccoli etc) and some companion annuals (alyssum, borage and I'm sure something else I'm forgetting right now), I sowed them in milk jugs a few weeks ago and plunked them on the porch. They're not taking up indoor real estate and they won't require as much attention until transplant time, I just need to keep them watered and if it gets too warm, open the jugs. They'll get a good head start being on the porch as it's warmer than direct sowing into the garden but won't require hardening off like the indoor plants will.

I'm not sure that really counts as wintersowing (as I didn't do it 'till spring this year) but other than the timing, I did it the same. It's an easy way to start seeds.

Here is a link that might be useful: Tales of a Transplanted Gardener

The other advantage to wintersowing, besides being less expensive than buying (what pathetic selection they have available) at the nursery, and also having the space to coddle seedlings all over inside--messing with supplemental lighting, etc., and that your plants will be hardier and already hardened off, is this: your plants will also be hardier through the hotter months, and more resistant to the cold at the end of season. My wintersown tomatillo survived a pretty hearty frost last year, but the indoor-start one (yes, same seed/variety) didn't make it.

However, one of the drawbacks is that, for some plants, there won't be enough head start to get big enough to get some harvest. For example, if you have longer-to-ripen tomatoes, they might not be ready to go before the first frost. Also, peppers will have a later start, etc., and something that didn't occur to me until a few days ago, is that my "120-day" okra (it's not really that long to harvest since it's a continual thing) will be so far behind the 8-ball that it might be August before we get our first okra, whereas if I have indoor or nursery starts, they are usually flowering in June. This might be particularly true if your actual growing season is shorter, like Bonnie's.

The other thing to remember is that not all things are suitable for true wintersowing--basil and some herbs are a little too intolerant of the cold that if they sprouted then there was a freeze, they might not make it. However, if you're starting now, I think you're good to go on just about anything from the cold-intolerant timetable.

That being said, I always start some stuff inside, and try to put it outside for as much natural sun during the day as possible, then bring it in at night until the nights are warmer. I do "backup" starts for the tomatoes that I can't live without (so then, will someone please explain to me how I have over 40 starts? Oh yeah... the SWAP!), and ALL my peppers and herbs--and certainly, the cherished okra. Also, I stupidly started some cipollini onions WAY too late (but I bought the seeds, and they'll be no good next year) inside, so we'll see if those guys turn out.

Of course, Trudi D will tell you that she started wintersowing as a great experiment because she was going cabin-crazy in the deep of winter and just wanted to make some mud pies in January... (My husband now wonders, since we move our tomato containers into the garage and harvest until February, if he will ever see his wife's fingernails without any dirt under them... I'm goin' with NO)

I thought I'd link to a much earlier post to give you an idea of what the thinking around here was, oh, all of 3 1/2 years ago . . .

I still haven't tried it.

Steve's digits

Here is a link that might be useful: Winter Sowing in RMG?

This is my second year winter sowing, and I must say for me the deciding factor was time. All I had to do was plunk some soil and seeds into recycled jugs, and hey presto! I had a lovely amount of hardy greens and flowers that came up when they were ready. No bringing plants in and out to harden them off. No checking for fungus or insects. It's great!

This year I'm trying tomatoes. Here's a link that shows that WS toms start off slow compared to indoor ones, but that they can catch up in a hurry (at least in zone 7)

Here is a link that might be useful: Winter Sowing VS. Traditional Seed Starting Trial

I've experimented with some different ways of winter sowing over the last 3 years. 3 years ago I winter sowed direct in the garden with plastic buckets with clear plastic over the top. It worked well overall. You never have to transplant that way. Then last year it didn't work as well and part of that was the year and part of it was me. This year I started 40 plants winter sown in flats in my cold frame. I waited to wet the potting mix till March 20th. Had sprouts popping up by April 1st. By the 10th had almost 100% germination on every variety but one. The same one that was slow and low inside. Those in the cold frame didn't grow as fast as those started inside the first ten days. As we were having cool nights. Now they are growing fast. And looking good. I will plant one wintersown by one started inside of the same variety so I can get a good comparison. So will be able to give some actual facts this fall. I'm still in the experimenting stage. Next year I will have a greenhouse. I will start some inside a cold frame inside the house. Will try to start them a little earlier. Don't plan on heating much if any. I've had others tell me that have done it this way. You can get them started at least 2-3 weeks earlier and being inside the greenhouse and also the cold frame the temp won't drop as low at night. My plan is too sow the seeds in dry mix in Jan-early Feb and wet the last of Feb-early March. Hope to have plants growing by mid March at the latest. Will install one vent in the cold frame in case temps rise too high. I feel the plants are more vigorous and healthy which makes them more disease tolerant in my opinion. Just trying to find ways to get some earlier growth and size on at least some of them. Jay

Okay, I guess you have me convinced. I'll try to get winter sowing going next year. I probably won't give up my indoor area just yet as I really like having plants growing in my office.