Just downloaded 1.5 a few minutes ago. The install went very smoothly. It needed to update some extensions. Other than that, it loaded and did not change all my settings.
(I have had some previous FF installs that ruined my settings; resetting them all can be a pain.)
It did not find some theme/extension updates until I ran the managers manually - I suggest manually checking for updates if you haven't already done so.
Yeah! Why is that? I hesitate to go to 1.5. I have tons of extensions and have to reconfigure the whole mess every freepin' time.
It's getting old real fast.