We stayed in a ryokan in Takayama a couple weeks ago, and it was absolutely frigid out in the halls, and in the vestibule area leading into our rooms. The toilet was in a separate room off the vestibule, and was not heated. Our room had a couple of heaters that kept the main rooms really warm, except for the first day, when something seemed to have gone haywire. We were worried at first that they allowed heat only at night, but it finally came back on. The onsen area was warm in the right places, and it was lovely to sit in the outdoor tub while gentle snow fell.

All in all, the temperature took some getting used to, but it was a fun experience.

Takayama was our choice for a midway point between Tokyo and Kyoto. It's about 2 extra hours off the main train line, but an hour of the trip up into the mountains is gorgeous, so well worth it. The town is well-preserved and very charming.