Yes, Firefox loads faster because of it's cleaner code.
IE takes a lot longer because of all the unnecessary stuff/crap that goes with it.
Firefox's program architecture/logic structure was obviously well thought-out, with faster pageloads as one of the objectives. They also avoided a lot of the logic flaws that give rise to many critical patches that IE continuously needs.
Firefox 3 Beta 4 is now out, and preliminary tests show it to be 3times faster than Firefox 2 and 5 times faster than IE7. Still, this is just a Beta release, so a lot more changes to it are coming.
