I am experienced in Diablo & Diablo 2. I completed Diablo 3 Normal mode.

I can't help but feel something is missing in Diablo 3. However, ppl who never played Diablo before might like this a lot.
Overall, I have mixed feeling with this game.

Story:
It is a bit rushed. I dun understand how Leah's father is Diablo. You mean her mother has s e x with a giant red demon???
Also, Tyrael looks bad, like an old Mexican... lol. At least make him look legendary face, like Qui Gon Jin in Star Wars.
The final Prime Evil feels stupid in the story. I never knew evil demon can be so dumb.
Very lacked of NPC development and story, perhaps it is because I am accustomed to Warcraft story.

Gameplay:
I like the skill animation. Enemy difficulty is pretty ok. Nightmare mode is interesting when running with friends.
Depth of the gameplay is a bit shallow for me. Diablo 2 gameplay is more detailed, allowing user to customize different build.
Why they take out the talent tree??? These can make the game more interesting and allow ppl to sell their characters in RMAH.
The D3 world is too small. Too linear. I expect side quests and as we progress to higher difficulty level, new areas are uunlocked.

Graphic:
Initially it feels weird. After a while, I think it is definitely more artistic than Diablo 2. But no more gothic horror feel.
Overall this direction is still acceptable for me.