It's running perfectly fine on my 64 bit windows 8.1 box in windowed mode at desktop resolution as well.
In my case I run a one year old machine that was built for win8 and I CAN run fullscreen up to desktop but fullscreen desktop for me runs "pokey" whereas fullscreen < desktop runs more or less normally
the game runs best windowed mode desktop
Read the thread just below this one "
Running the game windowed vs fullscreen " it explains our position on this issue
Don