Re: NVIDIA, please, fix Adobe Flash 10.2.x and 10.3.x
About the overlay problem (video leaking through anything that's black): go to text console (Alt+Ctrl+F2), get back to your Xorg (Alt-F1? Alt-F7?), problem disappears. Currently open Flash videos will turn grey and you'll need to close tabs with them, but then everything is ok. The same workaround also fixed other display problems I've had with nvidia driver on my GTX570.
About using hardware accelerated video: works flawlessly on YouTube, but FREEZES XORG on some own3d.tv videos. Solution is to kill Xorg (remotely or using SysRq combos), unfortunately that's not better than a reboot as I doubt you do stuff outside of the X session. I think I've had a freeze on justin.tv stream last week, but I'm not sure if I didn't try to watch something else at the same time. In any case, I've hashed out mms.cfg entries and the system is alive again.
Oh, and I also have an mp4 file that freezes Xorg when played with mplayer (using vo=gl, vo=xv doesn't have this problem) under 270.xx, but 260.xx are more stable and that's what I'm using.