I move between Camino and Firefox depending on sunspot activity, with a rare pause at Safari. For the past month I've been using Camino 1.5 pre-release on an ancient iBook (10.3.9), an iMac and an Intel iBook running 10.4.9. It's been great everywhere, fast, reliable, attractive. I sometimes miss Firefox's Google integration, but the OS integration, efficiency and performance outweigh that. I found only one ultra-obscure issue that would, I think, also occur with Firefox.
Now Camino 1.5 - is officially available.
There are almost no visible feature changes since 1.1. The big changes are spell checking, Keychain integration with Safari and excellent Gecko rendering. They don't have full OS X services integration however, for that you need to use the OS X text services and that's not compatible with Gecko. Camino also lacks the phishing protection built into Firefox.
So you get 90% of the OS integration of Safari with 100% of the rendering excellence of Firefox and performance that's at least as good as Safari. I almost never run into the CPU spikes that can force me to kill Firefox.