Thanks for the suggestions. Now that I have some free time I'll investigate the suggestions here and do some more research. Other than arriving/living via Frankfurt pretty much all my options are open.

It sounds like there are a number of interesting places to see within a reasonable train ride from Munich.

Since December is low season I just need to verify the castles/places are open. I know some, like Berchtesgaden is closed (I guess due to weather).

I'm also still pondering whether to stay in Bern or somewhere else in Switzerland. Bern seems pretty central to visiting a number of places (anything from Thun, Neuchatel, Lucerne, Lusanne, Interlaken). Staying somewhere more scenic usually involves less convenient train rides.

Heidelberg I won't rule out although I did a brief visit there in 2008.

Thanks.