There are four difficulty levels after Normal, and the game is designed to take one character through at least twice - the really good gear only starts to appear at the end of Normal, and some runes and skills don’t even open up until Nightmare. There are five classes that all play differently as well, from the revolting pets of the Witch Doctor to the dark ranged attacks of the Demon Hunter.
If anyone needs an explanation why to play Diablo 3 or why to play it more than once through, this is it. From Joystiq’s review.
I seem to have gotten my Diablo 3 in my WoW! Like chocolate and peanut butter, they belong together. In all seriousness, if you are looking for a lightweight themed interface for World of Warcraft as we approach the Diablo 3 release, this is the one. That way when you are playing WoW, you feel like you are in Diablo 3 and when you are in Diablo 3… ok you get it.
Find it here on WoWInterface (Roth UI by Zork): http://www.wowinterface.com/downloads/info9175-RothUIDiablo.html
Diablo 3 Beta: E2 - Pew Pew (Wizard Gameplay)
In episode 2, you will see the first few levels of the Wizard class and unlock a bunch of the initial abilities, which consists of a direct damage nuke, AoE (area of effect), wand, and a channeled frost spell (my favorite).
This is a bit long, but captures the beginning of the game (Monk class) through finding Deckard Cain. The monk class has had some nice animation improvement and skill tweaks - watch to see how they play out in the early levels.
Oh yeah and I do a pretty horrible Deckard Cain impression midway through.