Normally I wouldn't give a shit about installing this OS upgrade, except that apparently Apple has fucked up ScreenSaverEngine, so in order to make the XScreenSaver distribion work on 10.6, I have to do a 64-bit build of all of the savers... and that's not possible on 10.5, because the 10.5 version of the ScreenSaver.framework bundle doesn't include the x86_64 architecture.
How angry am I going to be if I install 10.6 on my only computer?
Will it break Photoshop, Illustrator and Lightroom?
The nature of Apple's screen saver fuckup is that .saver bundles aren't separate programs (like they are in XScreenSaver under X11) but instead are dynamically loaded code into the ScreenSaverEngine app. And now they've changed ScreenSaverEngine to a 64-bit app which refuses to load 32-bit code -- meaning they broke every third party .saver bundle.
Dynamically loading the code this was always an idiotic idea. Even before Apple's current fuck-up, it had already meant that one screen saver could screw up the namespace of one that happens to run later (e.g., there are some savers that you can't run consecutively in System Preferences); and it means that a buggy screen saver that hangs can make you need to power-cycle the computer, since deactivation requires the cooperation of the 3rd party saver itself, instead of that being handled at a higher level. With X11 XScreenSaver, user activity guns down the saver whether it is responsive or not: a sandbox, basically, which is the only sensible way to do it.
I'd volunteer to rewrite ScreenSaverEngine from scratch, to make it less flaky and more compatible, if I thought there was any chance Apple would accept and ship my contribution.
Update: Progress is being made. I have questions.