Re: VDPAU and KDE 4.8 compositing = slow
OK, with SMPlayer the problem is gone. The screen is still flashing green when switching to/from fullscreen, but it's very short and the desktop doesn't freeze.
I just noticed something however. The stuttering is not completely gone, but is directly related to the video's FPS. If I watch a 60FPS video, everything is smooth. If I watch a 30FPS video, the desktop is stuttering a bit. If I watch a 25FPS or 23.9FPS video (the majority of movies), then the desktop stutters even more. Not as bad as without the "queuetime" options set to 0 though.
And that only fixes mplayer. Which isn't really needed at all, because even with VDPAU and queuetime set to 0, Xv output is still much, much better, always resulting in a perfectly smooth video (VDPAU introduces a slight stutter/framedrops every two seconds or so.) The real problem with the VDPAU+composite slowness bug is Adobe Flash. It's useless right now.
I should mention that this is my first NVidia graphics card. I upgraded from a Radeon 4870 and was hoping to see the VDPAU support. I'm somewhat disappointed that it's not useful on a modern Linux desktop.