I finally upgraded Wumple.com from Fedora 6 to Fedora 10 several months ago. In case someone else runs into similar issues, here are the problems I encountered and solutions.
The Fedora install (via anaconda) did not upgrade many of the standard packages, so the subsequent startup had many errors (including missing shared libraries). I had to run a yum update afterward to update those packages.
Networking did not work. I tracked it down to /etc/dhclient-exit-hooks now needing to be executable to run, which is necessary for my configuration since the default route is set via the script using information provided by DHCP.
I had to update the motherboard BIOS due to lockups at the “Disabling IRQ #19” during shutdown. I found handy instructions for creating a boot CD here. This improved the situation but did not totally resolve it: I may need the “irqfixup” kernel boot option or may have to disable APIC in the motherboard BIOS.
Apache::MP3 (aka Namp), the music jukebox streaming system, needed additional modifications to run under Perl 5.10.0. Let me know if you’d like the diff.
The DMZS-sa-learn.pl script that learns spam and ham for SpamAssassin from a shared IMAP folder needed modifications to run. I updated the script to support SSL and batching to increase speed. Let me know if you need the diff.
SMTP AUTH for sendmail (via saslauthd) stopped working, resulting in saslauthd PAM errors in the log. I eventually found that I needed to remove the “required pam_stack.so” from /etc/pam.d/smtp or just copy /etc/pam.d/smtp.sendmail over it.
x10wish (the SmartHome PowerLinc USB driver for home automation) needed recompiled, and the source code and startup script needed some modifications. Again, let me know if you need the diff.
And that mostly took care of the problems! Good luck!