Steam is the best game distribution process known to man.
Ain't that the truth.
Though my one problem with steam, though its not actually their fault, is that when it comes to DRM so many people are completely confused. Many games use the same DRM that their CD/DVD counterparts use i.e. just about every EA game, a few use Steam exclusively as their DRM i.e. Dawn of War 2. And while this is all happening, there are many who seem to think that if its on Steam, that steam is the DRM and there's no DRMs they are opposed to aren't being used, so they buy the games and discover the truth the hard way and blame Valve.
Its a situation that shouldn't exist were both the game companies and Valve/Steam up front about it. Plenty of people would buy the games regardless, obviously some wouldn't, but I think the lies by omission aren't doing anyone any favors and making everyone involved look bad.
I won't bother getting into the whole DRM argument, other than to say many games, that otherwise would, just aren't separating me from my money over it, while other games I'd have never looked at before of are. I have my concerns, and until they're put to rest or, far more likely, proven right, my guard is up.
Does Running Crysis off your hard drive and steam hamper performance of the game? would running it off a disc be better?
Like one of the other guys mentioned, just about every game there is installs all its files straight to the hard drive and the only reason for needing the CD/DVD is for the CD/DVD check. If anything, running the steam version would probably be faster because there are times the CD/DVD check can take a needlessly long time.