I have a hard drive with all of the major OS X updates on it from Panther on up so I'm not too worried at the moment. However, I did have a disturbing experience trying to use my 10.6.8 updater after I reinstalled Snow Leopard from my 10.6.0 disk: the updater wouldn't work! I tried it twice and it failed (I forgot what the error message said). I think it detected a time stamp or something because when I went to download a "fresh" copy off of Apple's website it ran just fine. That's a load of crap if I've ever seen one: ticking OS update time bombs. Surely there's a hack around it...