I'm a Blizzard apologist--just to counteract the insane amounts of whining.
I think they knocked it out of the park with this game. Almost everything works as it should: leveling, environments, micro, economics (with some small tweaks), UI, hero diversity, etc.
Especially if you compare it to Starcraft or Wow at release, Diablo comes out looking real good--as one of their most complete releases.
What does that count for when the servers fall over as soon as you try to play it?