Interesting perspective, customization and optimization is fun. On that note there are a few UI customization programs that I find useful on OSX:

nocturne - invert or dim the screen, helps your eyes stay relaxed in different lighting situations: http://http://code.google.com/p/blacktree-nocturne/

divvy - quick window management, surprisingly handy, spaces becomes more useful with this as well: http://www.mizage.com/divvy/

visor - system-wide terminal via a hotkey: http://visor.binaryage.com/