Finished the game on normal with my monk, like most people, at lvl31. Way too easy with monk, didn't die once, pretty much just jump in click click click, use a few skills, and every mob dies, including the last boss.
The game is way short, in ~3 hrs last night I ran through half of act 3 and entire act 4. The entire game is probably less than 10 hrs.
Find it strange that there are very few side quests, just a few journals you can pickup, and maybe a couple can't miss quest that takes 1 minute to do along the way to complete the main quest. From the story point of view, D3 is really shallow. Also the skills, not sure what's the point since you get all the skill as you level anyway, it's just a matter which mouse button you assign to. As character development, since you don't choose attribute, you don't chose any skill tree, seems like the only thing that matters is the gear you have and which attribute the gear boost.
Definitely good action game, but not really deep on RPG component. (Is D3 even classified as an RPG?)