I just wanted to add that symlinking the WoW data folders instead of using separate installs will speed up quite a bit of the reads as well. I had a main directory with 2 separate directories for toons 2-5 previously non-symlinked and Shat was a killer back in the day. Once I symlinked the WoW data folder (as well as my interface folder...not necessary though), Shat gave me zero problems. This is all on a Raptor drive. I could only imagine the awesomeness of doing this on an SSD.

Dual Core with 4GB RAM fyi.