Jason, good idea for the demo on youtube. I'm realizing just how much of a luddite I must have been in the past few years, since I've had to teach myself all kinds of stuff that I think is usually common knowledge these days... like how to use Youtube :) The basics-- the maps are an open source topo map (opencyclemap) that most of the gps apps out there seem to use (like GaiaGPS and MotionX). As for the downloading of the map set, it's a pre-defined set of maps, so all you have to do is hit a button and let it go for a while. The whole set is around 400 MB, so it takes a while (I timed it at 25 minutes on my wifi connection), but you don't have to do it all at once.
Jeff-- I knew that was going to be one of the first questions... I'd love to make an Android version, but I don't have a timeline for that. I had to teach myself the iPhone programming language from scratch, and from what I understand Android is quite different. It's on my long-distance radar, but for now I'm going to try to get the iPhone version perfected before I branch out too much.