There is a great review of various nvidia cards, including the 9500gt,
comparing their performance on a variety of games and benchmarks using both
the latest nvidia binary blob and the latest nouveau drivers here:
http://www.phoronix.com/scan.php?page=article&item=nvidia_june_2012&num=1
As a general impression, the 9500gt didn't fare that much worse on nouveau
than on the binary blob. With faster cards though, there were gigantic
performance improvements using the binary blob over nouveau.
There is another nice, thorough article on the Phoronix site looking at how
well the very latest HD 4000 Intel Ivy Bridge integrated graphics chipset
works with GNU/Linux, too:
http://www.phoronix.com/scan.php?page=article&item=nvidia_june_2012&num=1
