Hello from Troy
I performed the upgrade install on my system (which is currently as follows - Gigabyte GA-Z68X-UD5-B3 motherboard, Intel Core i5 2500K cpu, 16 GB Corsair Vengeance DDR3 1600 RAM, 2 x 2 TB WD Green HDD's, DVD+/- RW, 2 x Gigabyte AMD R9 270 OC Edition graphics cards in CrossFire). It worked fine - although to be on the "safe" side I did create disk image files (.dmg) of my mavericks installation before I attempted the upgrade install of Yosemite.
Have you tried booting with -v -kext-dev-mode=1 to see where the KP is occurring ?? (and if so, is it possible to take a screenshot of the panic - it might help to find a solution to your problem. Also providing your system specifications could assist others (including myself) in helping you out
Many thanks from Troy