GPS has to be one of the most common threads on RV.net! They must be selling a ton of them. If you read through some of the previous posts about GPS units. Most people fall in 1 of 3 camps. 1. Go with the DEZL 760 (now with a RV version available). 2. The Rand McNally 7720 (Very Similar to the Good Sam GPS). 3. I am looking for the low cost leader with the NUVI 465LMT.
Some people look at the Magellans as well but they arent nearly as popular here on the forums.
Do a quick search of threads to find some good perspective if you dont end up getting a lot of replies here. It is heavily discussed in other recent posts.
A quick google search also shows these:
http://www.doityourselfrv.com/rv-gps-comparison-review-best-options/http://rv-roadtrips.thefuntimesguide.com/2007/08/rv_gps_info_for_rvers.php