I've been using Flip3D Activator for a few weeks now on both Vista and various flavours of Windows 7, (including 6801 x64), without any issues.
Only issue I've heard of with it is when someone set it to operate on a Left Mouse Button, and couldn't do anything that needed a left click
, so you have to be careful when assigning Mouse buttons
Other than that it's all good
I use the top left corner "Hotspot" and find that wherever my mouse is I can switch windows quickly either using the task bar or Flip3D,
It's also great for showing off
when someone's watching you