There are a few Nvidia specific features, but noone seems to care about them much.
3D vision, lightboost , and maybe gsync .
Doesnt anyone use 3dVision or lightboost?
Gsync is rather new, AMD has FreeSync on their side. How do these compare?
GSync is available as an add on mod to the Asus VG248QE monitor. It's $200 direct from nVidia for the G-Sync kit (They are out of stock currently.) and you have to install it yourself, or get a tech to do it. It voids your warranty. Their are some retailers you can buy The monitor from with the kit already installed or have them install the kit for you if you already own the compatible Asus model.
Digital Storm, for example, sells the monitors for $500 modified by them, or for $300 you can send them your monitor and they will do the mod for you. I'm not sure what sort of warranty they
(or others) offer.
G-Sync enabled monitors are supposed to be released by Asus (and I think BenQ) sometime in the 2nd quarter this year, if not delayed.
FreeSync is not AMD only. It's been incorporated into the latest DP standard (1.2a), so in theory should work on any monitor/GPU combo that is DP 1.2a compliant. The GPU would need driver support, but there's no licensing required by
VESA members (Thus why it's called "Free"), which AMD, Intel, and nVidia are (As well as others). There's been no announcements from any Monitor vendors of when they are going to offer supported monitors. The standard is very new only being ratified in the last few weeks.