Well I've played the game for several hours over the course of a few days, so here are some thoughts from the perspective of someone who never played the old Diablos.
I like Diablo III. Obviously since I never played Diablo II that means I have no rose-tinted glasses on. If I'm supposedly missing out on something because of what Blizzard did with the mechanics of the third game, I can't really say I notice. I don't care all that much about distributing attribute points, and while the lack of skill trees is a bit odd the rune system works well enough for what it is. I haven't really played many other games in this genre before because it never really interested me. I tried the first Torchlight a while back and quickly got bored with it, though the lack of multiplayer in that game probably had a lot to do with it. I imagine that if I was playing Diablo III by myself instead of with friends it wouldn't be nearly as much fun. Combat in dungeon crawlers is about as simple as it gets, and when I'm not playing socially I quickly become very aware of just how repetitive it is.
HOWEVER, that's still no reason to have always-online DRM. Just because I prefer to play with friends doesn't mean I'd NEVER want to play it by myself if I were to lose my internet connection for an extended period of time for whatever reason. I really don't care what Blizzard's excuse is, because it's inexcusable. Even if my connection never goes out, that still won't do me a damn bit of good when the servers get flooded with players as they inevitably did on launch day. Shipping this game with no offline single-player option of any kind was stupid at best and insulting at worst.
Moving on, the music (so far) is totally forgettable, but that's not really such a big deal to me. Games like this are rarely known for their soundtracks. The writing is absolutely atrocious, but I can still enjoy it in that schlocky B-movie kind of way so that doesn't really bother me either. The graphics are okay. They're not great, they're not terrible. The whole game is spent zoomed out in an isometric view anyway so fuck it. I don't play this for the music or story or graphics. I play it for the gameplay, and when it comes together just right it's a lot of fun.
I guess I just don't see what all these Blizzard fanboys are whining about. Except the DRM, of course. That part IS bullshit.