Mozilla Firefox is my browser of choice. Version 3.5 is now official. Download link. Or if you already are using Firefox, you can choose Check for Updates from the Help menu.
One minor warning. When I updated, the install program warned me that the current versions of some of my add-ons are incompatible with version 3.5 and therefore will no longer work unless they too are updated. Indeed, the install program listed those add-ons, and offered to check for updates to them. I accepted the offer of course. Alas, only one of the add-ons had an update that made it compatible with version 3.5. The other ones were disabled automatically. Presumably (hopefully) most of the other add-ons will be updated soon now the 3.5 is official.
So the moral of the story is if certain add-ons are critical to your use of Firefox – and they are for some – then check their compatibility with version 3.5 before you upgrade Firefox.