Since this optimized version is built on the official 1.0 release, all of your extensions and other tweaks should still work. He's also included Kevin Gerich's pretty widgets, which, though not native, are about 10 times better looking than the stock widgets
If you have a newer G4, you're not left out in the cold, either. Neil links to Kai Rune's G4-optimized Firefox build. I've been using this one on my PowerBook, also with no issues. Finally, if you'd like to build your own Firefox from source, an anonymous reader sent in a pointer to this set of instructions (which I have not tested).
With both apps, you'll have to live with a (different but cool) icon, as only official builds are allowed to use the Firefox icon. If it bothers you too much, though, just paste the standard Firefox icon in its place!

