Firefox 3.6 went final last Friday, so I'm moving to that at my "regular" version of Firefox, replacing 3.5. I've been using the 3.6 Namoroka PowerPC G4 build for some time, and it's been very stable.
I wanted to put the 3.7 alpha on my Power Macs and soon discovered that it won't launch on Mac OS X 10.4 "Tiger" - it apparently requires 10.5 "Leopard" or later. That's a shame, as Tiger remains a great operating system and meets almost all of my needs. (Ditto for Leopard, which doesn't support Classic Mode. That's why I use two Macs side by side.)
Camino 2.0.1 remains my primary browser, with the PowerPC build of Firefox 3.7 playing second fiddle. I also use Opera 10 and Safari now and then.