In fact, all went better than well. I observed something pretty odd: The /dev/input/mice which was before just for USB mice now is a generic interface to all mice. I forgot to include USB UHCI support (the config name changed and I didn't notice), so when X started, my mouse worked, except for the scrollwheel. Turns out my BIOS was faking the USB mouse, making it look like a PS/2 device, which the kernel knew about, and reported the events down /dev/input/mice, which my X config was still setup to read. The mouse resolution sucked, but it worked. Rebooted after adding UHCI support and it's all smooth and I can scroll. Very cool.
Half-way through this excercise I justified it as work: all the LJ web nodes netboot in the exact same config as my home computer, so if it works here, the LJ web nodes are ready for 2.6. (which is actually convenient, since epoll is included in 2.6 and we wouldn't have to keep applying patches)