I upgraded my dev box to Fedora Core 9 yesterday, which mostly worked well (except, it botched the grub boot loader, and failed to upgrade ~4GB's worth of FC6 packages). Most things went well, except the migration to PulseAudio. It ended up starting in a "broken" state, and then Gnome gets really unhappy (including any Gnome apps). Looking in syslog, I'd see

May 18 22:57:05 loki pulseaudio[2733]: main.c: Called SUID root and real-time/high-priority scheduling was
requested in the configuration. However, we lack the necessary priviliges:
May 18 22:57:05 loki pulseaudio[2733]: main.c: We are not in group 'pulse-rt' and PolicyKit refuse to grant us
priviliges. Dropping SUID again.

Adding my user to the pulse-rt group seems to have fixed this particular problem, so things are happy again. Getting Firefox and Flash to work was a whole different story, doing a number of web searches, a few suggestions to use libflashsupport. However, digging deeper, setting the environment variable FIREFOX_DSP also does the trick. E.g. something like this in your firefox startup script:

export FIREFOX_DSP="aoss"