Actually it's just that it supports the 3200+ properly. You could always use 400MHz bus on this board.

Since the PCI/AGP clocks were locked, there's really no difference I presume other than timing tweaks and proper display of the 3200+ rating.
Oh yeah, you might look here too:
http://www.nforcershq.com/forum/viewtopic.php?t=15505
Enables a bunch of settings Asus doesn't. The revision list from Asus also does point to the change just being to recognize newer CPUs (plus some other stuff that I'm sure many people will be pleased to see).