Haven't used Linux for ages. Under Windows I can have a deluxe NVIDIA driver installed right now.
The blob has the same performance in linux as in windows, games generally yield the same performance too, except for some that use a wrapper without decent optimization. See here for a januari test - http://www.phoronix.com/scan.p... The nvidia header file releases discussed in this article and their future plans might boost the opensource driver linux though, which performs badly.