There are two things i don't like about the rb1. The first is the screen size, it's so small that even on the highest zoom, a lot of the street names aren't displayed. Working in an unfamiliar city, i use the map feature a lot to get around, and the rb1's screen makes it tough.
The second is that if you want to listen to a cd and use the nav at the same time, you need the rear changer. (Or an ipod and ipod adapter for ripped cds).
This is just my opinion, but DCX has done a poor job with navigation systems overall. the next generation REC nav system wont with our KJs (if somebody knows what wouldn't work by having a different CAN system, i am curious to know). And the newest generation nav (RER) finally has a touch screen and hard drive...and it will work with no model 2006 and previous vehicle. The only 2007s it works with are Dodge Nitro, Chrysler Sebring and some Wranglers.
Sorry about the rant, the nav system is the only part of my KJ i'm very disappointed in. And it was by far my most expensive mod.