I have the Dezl 760 and overall like it very much. That said, it has it's limits and you should be careful with what it tells you. One time in Maine it took me on a VERY problematic route to avoid a hazard. Luckily I was not towing at the time (even though it was left in RV mode), or I never would have made it through the narrow residential streets it sent me on.
It also tried to send me 200 miles out of the way to avoid a tunnel hazard on the Oregon coast, which I ignored. Turns out the edge of the tunnel was below minimum, but the peak of the arch was 4 feet higher. I was in terror as it kept warning me about the upcoming low clearance, but I kept seeing units taller than mine coming the other way....
There are a lot of places where it tells me that hazard data does not exist, so I end up having to cross my fingers there is nothing ahead that will cause problems, but they are obvious areas where there is no concern anyway.
I also have the Rand-McNally version on my iPad, and can't say in the above respects it is any better. I find operating the Dezl to be much better. Love the "lane assist" feature that tells you ahead of time which lane to get in to. Saved me in Chicago multiple times!