I am amazed by the negative comments. I have had a RM 7710 for over a year and have driven over 12,000 miles with it, and I have found it to be excellent. I've had no major routing issues, and the only mechanical issue was a loose power connector, which is a problem on some 7710's but has been changed on the later models.
I find it particlarly easy to find RV type places such as rest areas, Flying J's, and Walmarts. The campground database is far better than on the Garmin that I used before. I like it so much that I am in the process of trading it up for a 7720.
I met the design engineer and he is an RVer who knows waht we want and need in a nav unit.