1. If you got the scratch for an iProduct, then pony up the dough for a real GPS.
2. Those maps are only as good as the people programming/uploading them. And I've seen a bunch of instances when they were just plain wrong.
3. You'll learn the roads better by riding them. Mapquest gonna tell you where the 'Ghetto' is at?
4. INCOG has a bunch of info about all of the trails/MUPs and designated bike routes in town.