Hi Till.

First: Congratulations, you got more of a responce from teleAtlas than I got.

You are right that GMF data discs seem to be easily available. BUT if I read the (german) discription of those maps that I found at http://www.poly-electronic.ch/cd-karten.htm correctly, those aren't intended for real navigation tasks in the way we want it, but rather those are for moving map applications (read: rasterized maps, not vector based). Also, the map format doesn't seem to be well documented.
GDF maps would be different though, they are really well documented. Rather hard (or expensive) to get, though.

cu,
sven (just started working his way through the GDF documentation)