Sword Art Online is an interesting story that takes some getting used to. The second arc, "Fairy Dance," seems more than a little rushed, but this really can't be helped considering the timeframe that Kirito has to work with.
The animation quality is average -- nothing too exceptional, but Aincrad (the first fourteen episodes) is stunningly gorgeous from start to finish. Again, the second arc really falls apart in this department, but this is probably because it has so much to live up to.
Character development is an interesting thing to think about in SAO. It isn't perfect -- and by any extension, it has plenty of flaws. At the same time, however, Kirito's character is authentic and relatable in his feelings for Asuna, and that ultimately drives the show home for me. There are some characters that are annoying, and just plain outright creepy and offputting, but this is a story about Kirito and Asuna. If they had less screen time for the sake of developing other characters, I wouldn't have enjoyed it as much.
The thing that sets Sword Art Online apart from the rest is its first arc. Aincrad is a stunning world, and by forcing players to live in an MMO, every point about the world is unique and clever. This is not a show for children, but a show that emphasizes just how far some people will go for the sake of morality and love. In a way, Fairy Dance, the second half of the show, is a lot more about temptation and holding on, despite almost certain failure.
Sword Art Online is a show that doesn't leave a lot in the plot department up for inference. What it does do is deliver an exciting story that is executed perfectly for what it had to work with. It delivers a punch, and whether or not the story will stay with you to the end, Kirito and Asuna will. If you're on the fence, jump over and watch. Even if you aren't, give it a try anyway.