using the pip hot key when I was running Vista 64 with Keyclone I was experiencing really slower then I should (or so i thought for my system); then I upgrraded to Windows 7 and it runs a lot smoother.

If your still having issues then do try the following(stuff I had to do to even get WoW to run decent on my laptop with vista period)

Right click shortcut or wow.exe -> properties

Compatibilty tab-> run as Windows XP

disable vista theme and run as administrator

hope this helps