I just upgraded to Windows 8 a few days ago and am going through the Assassin's Creed series. In Revelations particularly in the masyaf key locations it freezes momentarily and then becomes fine but repeats again. It is really messing with my gameplay. I have played it before in windows 7 without any issues. If it is any help when I played in Windows 7 the game was downloaded from the internet . The current one is from a dvd I bought.
My rig is :
Intel Core i3
6gb ram
500gb HDD with 1TB External
Sapphire HD 7750 with latest driver (13.9)
Thermaltake 750W PSU