I used to use Deer Park. It has been out for a while now. I stopped using it because it gets buggy when you are using Java applications and there are some other bugs. Best to stick with FF 1.0.4 for now
i think its cool.. not having firefox in the first place, seems nice... im on a 3.8 mghz comp with about 3 gigs of ram... very fast speed indeed.
Can't tell much difference from FF, but it is only a Beta version at the moment. Could be sweet when they're done.