Anyone been to Germany? Worth going?

Best way to go (IMO) is when there is a base of operation to work from. It sounds like that type of arrangement. You've be visiting them and getting to know the area - taking day trips on your own pace as opposed to some rush rush running everywhere.

When you get there, or before, see what's in the area that matches up with your interests. Anything from art museums to car museums, or some hiking and beer. Beer's easy, just say ien beer, bitta. :)