Patrick, I downloaded Mozilla 1.0RC1 the other night, tested it for half an hour, and had the exact opposite experience as you did. On my system (600 MHz 14" iBook), IE5 seemed much snappier. If you are using a desktop system, I wonder if the speed of rendering has something to do with the graphics card in the computer (the iBook has a wimpy one) or, God forbid, the L2 cache size (the iBook design has a small L2 cache for some asinine reason).

Fortunately, both browsers are free, easy to install, and easy to test against each other.