I am currently on Firefox 3.6 which generally serves me well (compared to IE anyway). I have just received an email from Yahoo urging me to upgrade to Firefox 4, promising faster downloading. I am sure I have read on this site that some people have had problems with Firefox 4. Any thoughts from the experts, as I would rather stick with the status quo than cause further difficulties.
I've been using it since the beta and find it fine. some of the buttons have moved about a bit but they can soon be moved back if you want and you'll find a few add ons won't run on 4 so it's worth checking if there's any add-ons you see as a must have that won't work.
Other than that it's certainly faster, but for browsing, not downloading, there is no way a browser can give you faster downloads.
I have been using FF4 for several months and have had no problems. On the other hand it has not improved my love life, freshened my breath, or cured my miscellaneous aches and pains, (nor is it noticeably faster) so if 3.6 makes you happy I do not see a compelling reason to switch, either.
Thanks to all for the prompt and expert advice. Seems unanimous. However I think in my case Bib's advice is the most sensible, if a new version is coming out in a week. Warning, I may be back in 7 days!