I'd had both Firefox 3.0.11 and 3.5 Beta (aka:Shiretoko) installed in Jaunty. When the update showed up for 3.5 yesterday it installed with no problems so I removed the Beta version using synaptic. (After transferring my bookmarks-places.sqlite)
I then ran apt-get -f install from terminal which indicated to autoremove xulrunner 1.9.1 which I did and I noticed no regression, but I'm just curious what version xulrunner you recommend?
I tried to read the changelogs at the PPA for firefox daily:
https://launchpad.net/~ubuntu-mozilla-daily/+archive/ppa
But it's far beyond my intelligence level. So I'm just curious. No rush.
I also ran the update on Hardy and all seemed to go flawlessly. I didn't think to look and see but I'm sure it's still using xulrunner 1.9.
I'm uploading some torrents right now so I won't be able to reboot for a few hours.