So after running this app and doing some navigation training I can say it is really good. The mileage is spot on, especially when running a mapbook created with Rally Navigator (since it uses GPS based mileage calculations also). The cap is spot on and is quicker to respond than a Garmin GPS. There was some detected magnetic interference from the bike at times but only when stopped. Overall pretty impressed. Now I just have to dial in a way to power the Iphone from the bike. Some of the cheap Chinese crap I bought didn't get it done.
On the Iphone 4 running os6 there is some color issues on the reset/zero screen (can't see the letters in the buttons till you touch them but I memorized it.