Running OS X, I just got an upgrade from 2GB to 4GB of RAM. I wouldn't have bothered--just running the OS, Eclipse etc. is fine--but when I'm running Photoshop

Running OS X, I just got an upgrade from 2GB to 4GB of RAM. I wouldn't have bothered--just running the OS, Eclipse etc. is fine--but when I'm running Photoshop and an instance of XP under VMWare Fusion, things start getting a little sluggish.