Apon trying the latest -bk, I've noticed changes in how the kernel
determines mouse rate.
Although this was easy to fix with gpm, XFree86-HEAD does not seem to
honor any manual overriding of the mouse rate. Even when setting the rate
to 60 this did not work.
After reverting the psmouse-base.c changes XFree86 behaved like previous.
I would suggest reverting the patch until this issue is resolved. I don't
know what X is doing to get the mouse rate but it certainly ignored it
when I set psmouse_rate=60 in kernel parameters. Perhaps someone knows
something I'm not doing...