If anyone has had any problems with PHP 5 final and the $_SERVER['PHP_AUTH_USER'] variable, there's a simple solution. In the next few days or so, they will be releasing PHP 5.0.1 (or hopefully they will), but until then, you can get the snapshot of 5.0.1 from http://snaps.php.net.
The bug can mess up phpMyAdmin and many other programs that require user authentification. In my case, Apache kept shutting down every time I went to a page that requested $_SERVER['PHP_AUTH_USER'].
For more information on the bug: http://bugs.php.net/bug.php?id=29132
For latest CVS snapshot: http://snaps.php.net/php5-latest.tar.gz
For the latest Win32 binaries: http://snaps.php.net/win32/php5-win32-latest.zip
I have it up and running on my server: http://potatosalad.gotdns.com/serverinfo.php and as you can see, it says PHP 5.0.1-dev. Hopefully in the next few days they'll release an official build. That was a pretty darn big bug for them to "miss." Something must have gone wrong during the build or something. They should have caught this earlier.