Here is an awesome vid of KAIL (one of the DMC gameplay Gods simply put) playing DMC3. You should get a good look at how DMC4 will play, since the gameplay will remain the essentially same fast paced combo-chaining action.
Even if you're not interested I advise you to take a look. It just looks insane. I'm pretty good myself but compared to this guy I'm nothing.
Also, I should add, it's harder to pull that stuff off then it looks (it doesn't look that easy anyway, but still).