Anybody use TomTom or other preloaded map apps?

I am going on a trip to the mountains of North Carolina, and I'm looking for an iOS maps app that will let me preload a large amount of maps because I'll be in non-cellular signal territory. <insert AT&T joke here>.

Looks like MotionX GPS Drive lets users preload a small area, but I'm not sure if it'll be enough. Apparently they are bound by map vendors to keep the preloaded map area small.

I could go for TomTom, but that's a relatively large cost and I'd like to hear some user experiences with it. It's not highly rated in the App Store.

Any others?