I did an upgrade install, no archive, and afterwards found some strangeness with X11 and Fink software.
First problem: The X11 application had been moved from Applications to Applications -> Utilities, but would insta-crash on launch. Solution: trash ~/Library -> Preferences -> com.apple.x11.plist. Simple!
Second problem: Can't launch The Gimp (or any other Fink-installed software, for that matter). Solution: realizing that although my shell is still tcsh, Apple changed which file is read on startup from .cshrc to .tcshrc. Copying the relevant source /sw/bin/init.csh line into the new file solved the problem.
Hope that helps someone!
Mac OS X Hints
http://hints.macworld.com/article.php?story=20031029200403209