Haven't tried 196.21, but was testing 195.62 on win7-64HP. Worked well for a while, but then started failing on the driver - 'Nvidia driver has stopped responding but has successfully recovered'.
Every time this happens, it seems to 'forget' the current GPU WU, and start another. I have a GTX260 and an 8800GTX in this machine. When it failed 3 times in less than an hour today, I went back to version 191.07. No problems since, and I was using BBC iPlayer to watch recorded TV as well.
My other machine is a Vista32HP. That one didn't seem to be failing in the same way, but I still went back to 191.07 on that one too. It only has one 9800GTX+ in it.
If you really need H/W Flash acceleration, then try it. I got fed up of the increasing unfinished work units. I may try 196.21 in a while if it seems to be stable for others.
195.62 just wasn't stable enough for me.
regards, Gizbar.