I played it on 360 at a friends house and it was VERY stiff...but I own it on PSP and it was quite fluid. My guess is because it was ported to 360, but made for the PS3 hardware even in the arcade version (I know for a fact that that much is true, but maybe its the REASON its so stiff) and with the PSP one, it was based off of the previous psp tekken and just modified to be Tekken 6..so out of the 3 versions, only the 360 one is truly a "port" as opposed to being made from the ground up for the sysystem its on, like the others. That's my only guess as to the REASON its so stiff on 360.