If it's the same as the 07-10 JK's RER MYGIG navigation head end, I'd give it a 4 or a 5 out of 10. Not totally useless and, as pointed out, there are some trails in it, though the logic of what gets shown and what's empty white space defies analysis, or at least my analysis. And there is a semi-cool "bread crumb" feature that's handy, especially when you're in one of those white areas. And it has fast boot up, and the audio part has some nice features. You might decide (I did) to spend even more money for the Lockpick add-on so you can add features, like backup camera capability, that Mopar should have built in.
It is, on the other hand, a pretty clunky, inelegant unit. The user interface and the not-very-high resolution graphics strike me as sort of turn-of-the-century, and the maps never seem to have enough detail or be at the optimum zoom. All in all, there are lots of prettier units.
photo: jeep.com
But it works, and everything (radio, nav, hard drive, USB, aux in, sat radio, bluetooth, etc.) is integrated into the system, which counts for quite a bit in my book. But running a separate off-road nav program is probably way better if you have an ongoing need for serious off-road direction finding.