TLDR: Something's very fishy with yesterday's updates, you'd better stay away!
Well, installed both the cumulative Windows 10 update (KB3120677) and firmware update yesterday on my Surface Book, and now neither the pen, nor trackpad are working or being recognized. There are four unrecognized devices listed under Other Devices, and no amount of "update driver" helps.
This comes on top of Calendar and Mail crashing continuously on startup which began happening after that update too.
Prior to the update, the Book perfectly fine. Yes, it had that Intel driver crashing in Edge all the time, but at least the trackpad and the pad were usable.
UPDATE: After reboot didn't help, tried resetting with Power+Volume combo. The mouse disappeared at all and trackpad stopped being recognized. Detached the Clipboard, which worked, then attached it back. Suddenly both the pen and the trackpad got back online.