So.. It appears that 10.5.6 has messed up a lot of peoples performance under the 9600GT. I just took notice this afternoon when playing back the 1080p trailer of the "Journal" found here http://www.apple.com/trailers/wb/watchmen/ . What is more interesting is playback is FINE when using the lower performance 9400m. For those of you who would like to test this, watch this clip under "high performance" in energy saver preferences, and again under "battery saver". Post if the playback is choppy under either of the two. Click on "Journal" then 1080p here http://www.apple.com/trailers/wb/watchmen/ If this is true for all MBP owners, then there is either a driver issue here or a hardware issue. Lets use this thread to try and narrow this problem down and get a solution.