Finally! Corey found m200 drivers for Vista that were released on 3/20/2007 on the Swiss support site. The page is not English, but as Corey said it's pretty easy to figure out. (The drivers themselves have english versions).
That said, here are the direct links:
I installed the other day and so far everything is great (i.e., as it was on Windows XP). Full 32-bit at 1400x1050 with (automatic) screen rotation, sleep/hibernate work properly, and the Tablet PC buttons work again.
I have to admit, I was worried we really would never get these - after all, Toshiba doesn't always have the best track record for supporting products it doesn't care about anymore. Still, it would anger me more that they had them and chose to withhold them than not spending the resources to port them in the first place.