Last month we used our Good Sam/Rand McNally GPS for a cross-country trek - Colorado to Georgia, and return. Unfortunately, we were traveling without the TT (staying with family).
The GPS worked like a charm. The main criticism I have is the speed limit it displays is often not accurate with the locally posted speed limit. This is not just occasionally, but a regular occurrence. I'm not sure why it's this way. In all other respects, we're really happy with the GPS.
Don