After running with 256.44 for a few hours, graphics gets super slow. Like switching windows takes on the order of /seconds/ even just switching focus to a different existing window can take a second or more.
I have found that switching to a vt and back will temporarily speed things back up, but it only lasts for a little while. cpu usage doesn't seem out of the ordinary, nor does memory use. 2G out of 4G used, either with lots of (actual) free mem, or with it all filled with cache.
In case it helps, my nvidia-bug-report log is here
TL;DR log details:
Distro: Debian Sid
Kernel: liquorix based 2.6.35 amd64
X: X.Org X Server 1.7.7
Nvidia drivers: 256.44 amd64
Desktop: KDE with kwin gl compositing
Monitor1: 24" 1920x1080p LCD
Monitor2: 21" 1600x1200 CRT
Desktop Setup: Primary Monitor1 / Monitor2 RightOf Monitor1