I too have been an OS X user since day one, and this update is the worst I've ever installed. 10.6.0 broke a few apps, but that was understandable. All in all it was stable and nothing odd happened. After installing the 10.6.1 update I've been having hangs every few hours lasting about 30 seconds. Unfortunately it freezes Activity Monitor so I have no idea which process is causing the hang. It also changed some of Finder's prefs, turning on "Empty Trash securely" among other things. It even truncated some of my Safari bookmarks. If you haven't installed this update, it might be a good idea to wait for 10.6.2.