Overclockability, the fact that it has support for 800+mhz Memory, 2+ PCI Express 16x slots for SLI/etc, both PCI-Express slots are 16x.
Plus, Gigabyte has good following in the motherboard community. If I am going to go as far as to get a new motherboard and the works, I want to have a motherboard that will be capable of being upgraded for awhile.
I actually change my mind to the:
GIGABYTE GA-X38-DS4 LGA 775 Intel X38 ATX Intel Motherboard
and look into getting 4gigs of Kingston Hyper-X DDR2 1200mhz RAM.
Would definitely call for some intense cooling if I also overclocked the q6600, the ram, and the two SLI'd cards. And I do game at fairly high resolutions.