After watching the gameplay videos, I have to say that this is the first game in a Loooong time that I am truly PSYCHED for.
In fact I think this game has the oomph necessary to give PC gaming a big boost right when it needs it the most. And if anything, this IS the 'killer app' of the current generation that will get people to upgrade to at least a decent PC setup. (Not Crysis level uber, just something current gen decent.)
And I'm not sure anyone else really noticed, but check the gameplay trailer again and look at where the shortcut bar and health/mana balls are...middle of the screen. I think this shows that D3 will be a "Widescreen" game. And that regular 4:3 support will be included, but will 'encourage' people to upgrade their graphics/monitor to get the 'full experience' even if they don't upgrade their CPU.
I think Diablo 3 has a good chance at having as big an impact on gaming as GTA IV and MGS4, if not more of one.