thunderbird:
I would make sure that your graphics card is able to handle the new flash. I know that my graphics card is not updated enough to use the new Flash Player 10.1 Beta. This is stated by NVIDIA on there website.
I have a 6800GT which also isn't technically supported by the newest driver update geared for Flash 10.1B, but I believe that support is for a certain type of video decoding. One can still install the updated Flash player, but it just won't have that added functionality/improvement provided by the driver upgrade.
I played a few rounds with the update last night and didn't really see much of a difference in terms of swing meter consistency. CPU loads were down a bit, maybe around 10% or so, which was a plus.
Swing meter consistency seemed better when I turned off hardware acceleration in Flash (which is somewhat counter-intuitive), but I only played a few rounds with that setting off, so it could just be coincidence or luck. Could also be a driver issue/interaction with the Flash 10.1B.