I recently bought a paper wheel knife sharpening system. Here are my initial impressions:

Pros: Man, does this thing make knives SHARP! Whoa. Pretty easy to learn; by my second knife I made an edge which would shave the hairs off my forearm. The last one I did, an old heavy thick meat cleaver, ended up with an edge which easily sliced a 1/8 thick slice of an overripe tomato.

I learned how to use a whetstone when I was a kid, and could occasionally get an edge close to what these wheels did, but it took forever. That's the other advantage of this system,it's really quick: even the dullest knife only took a few minutes to sharpen up.

Cons: While the total cost isn't that great (~$40 for the wheels, another $30-$50 for a dedicated grinder (I found a cheapo at Big Lots for $20, works fine)) the best setup might be to have a spot in your workshop or utility room for this. As you use it it spits off little bits of gunk (wax + grit)and it makes the counter around it a little messy. That's not a major complaint, though; cleanup didn't take that long. Next time I'll put newspaper under it.

If you have the storage space or work space for it, I highly recommend it. If you have a tiny kitchen and no storage, don't get it.

The link is to the website where I bought the wheels. You can also buy an inexpensive book there on sharpening, although the instructions for use for the wheels are more than enough to learn how to use them.

The guy who runs the website reviews other sharpening gadgets as well.

Full Disclosure: I have no financial interest in this website or these products. I liked the performance of this item and thought I'd share my impressions.

Here is a link that might be useful: paper wheel and other sharpeners