I think it's using Birdie2k for the window patterns, and Visual Prefs for gadgets, etc. Alternatively there's also AFA_OS which will add that and more (anti aliased true type fonts and 32bit dual state png icons for example). Using Birdie and VP is a little lighter, and can achieve some nice results still, but if you dont mind using some cpu resources for aesthetics I'd go for AFA_OS.
