You're damn right Mozilla is fast!
It has really improved in recent versions. I'm using a CVS pull from last week that I compiled with -O5 -march=i686 flags, and it really screams along! If only flash for linux could be this fast...
If you REALLY want some serious speed, however, you should forget graphical browsers altogether and get yourself a copy of Links. It works on pretty much any OS with any sort of POSIX compatibility and a C compiler, and it is so fast you won't know what to think! I'm posting from it right now! 🙂