pparks1, WindowBlinds version 5 and 6 were known to cause slow down. However, from what I read, version 7 is a complete opposite of the older versions and was completely re-written. Heck, I read that WindowBlinds "overrides" the Windows GDI layer and, let me quote, "and is actually four times more efficient at rendering hardware-accelerated windows". Source
I kind of want to skin Windows because I'm getting a bit sick of seeing the good ol' windows and wanted to spice it quite a bit.