Was not a fan of this game on PC; largely under featured compared to its predecessor, which made it a big disappointment (to be fair, got it on sale for $20, so I can't complain too loudly; definitely worth $20). However, this game translates really well to couch co-op. I couldn't believe it, but my wife really enjoyed the demo, and we've gotten pretty far into the game on our second playthrough!
Not sure if it becoming a casual xbox game is what I would've wanted from the series, but hey, again, it's a GREAT game to sit in front of the TV with. Definitely rare to find good couch co-op games nowadays, so if you're looking for a game you can play with some friends or the other half that has some sort of consistency (levelling up, grinding up new gear, etc), D3 is definitely a pretty great game. I bought it for $40, so I thought that was fair, though to be honest I wouldn't pay the $60 it normally goes for.
Fans of the series, just take it at face value and enjoy it for what it is. As long as you leave D2 in your nostalgia vault, you'll be able to appreciate the fun there is to be had here.