"Fixed a bug that caused extremely slow rendering of OpenGL applications on X screens other than screen 0 when using a compositing manager."Well that sounds nice. Hands up who runs compiz on an nvidia card with two screens using xinerama? You might notice your GL screensavers run incredibly slow. Here's some examples, for testing I used glmatrix which you might be able to run directly via /usr/lib/misc/xscreensaver/glmatrix.
I have a Core(TM)2 Duo CPU T9500 @ 2.60GHz laptop with an nVidia Quadro FX 1600M, 1920x1200 screen and a second 1920x1200 LCD. I've loaded the new 256.53 nvidia module. Here are the results: