I don't really consider deviantART to be that great a site. There's a lot of backbiting and flame wars and butthurt and ego bruising and "ITZ MY STYLE!!11! U KANT CRITIQUE MY STYLE!!11!" and other stuff that makes it seem more like high school than a community of artists. If I was really looking to develop as an artist, I'd hang out on conceptart.org which has people who really know their shit. Their critiques can be a bit brutal, but out of honesty. They aren't looking to pick on anyone, they are just stating the unsoaped truth so you know where you need to improve. It's a wake-up call there, but in a good way. By signing up there, it is implied you want to get better and they will tell you how (throw your ego around, though, and they won't hesitate to pwn your ass).
deviantART does accomplish one thing. On the days when I think I'm fooling myself about being an artist, that I have no business trying this, that I should just put away the pages and never set pen to paper again until the Second Coming, I think about the people on deviantART who get 100,000 page views. I don't mean the ones that usually languish in obscurity until they draw fanart of popular series (Inuyasha, Sonic The Hedgehog, etc.) or pr0n, and get page views, meaning they are great artists, but no one really cares unless they are catering to their whims. I'm talking about specific people who clearly cannot draw. One person drew a furry "character" that was a stick figure with cat ears and two breasts, depicted as one circle with a dot in the center each and just under the armpits. One viewer commented, "Wow! It's a cat stuck in a dough sheeter!"
And then, there's people like the (now deleted) Chase The Hedgehog. He got 100,000 page views for his Sonic fanart. Here's a representative sample:
Nineteen years old when he drew this. Nine. Teen. 100,000 page views, folks. Just ask him, he'll tell you aaaaaaaaall about it.
And then I look at my art, like this piece I call Polka Party:
...and I feel a lot better about myself....