I read the first volume of the Sword Art Online manga, and it was pretty good!
I have now started watching the anime. MISTAKE. First episode was fine, but the second episode... I felt embarrassed watching it. I don't know which is more accurate to the original novels, but it was nothing even remotely like the manga. In the anime, Asuna is some nobody with a bit of skill, which is very different from the manga, and Kirito is, uh, odd.
But, what bothered me most of all, was it takes the same approach other MMO-animes have done: the MMO aspects make no sense. Obviously I'm approaching this as someone who, like lots of you guys, have played many MMOs. Many of the mechanics described in SAO just make zero sense. It's frustrating.
If any of that changes, feel free to let me know, but otherwise, I think I'll stop watching.