I have tried many, many online games in my time, and only a few have ever kept me interested for more than 20 minutes.
Graphics: To me graphics, in any game are not as important as other things. Sure, they help make a game, but I can play text games with music just fine and have a really good time. WoW's graphics may not be state-of-the art, but they are impressive. The graphics do seem slightly (And I mean slightly) dated, but the animations of the characters are the best I have seen yet in an online game. They look like a midieval style game should look.
Sound: Sound and music are big time needs to me in games. If there is no sound, I turn my own music on (which, even if there is sound, I do sometimes because it is repetitive and redundant) but that isn't the case here, the ambient sounds, the music, it pulls you into the world.
Gameplay: This game is easy to get in and play which is a good thing for any game. One online game I played had a really difficult interface, and I spent about an hour working out how the thing worked. With this game I knew the interface and how it worked within five minutes.
Final word: This game is a reccomendation for anyone who likes MMORPGs.