I take it that MotionX is dependent upon the wireless carriers signal, which means that it's not so great, in my case. AT&T is, uh, not so hot around here. On my ride around the park, today, MotionX shorted me about 2 miles over a 43 mile ride. Part of the problem is the network/signal strength - about a half-dozen times (that I noticed) the nice narrator lady notified me that the phone had lost the GPS connection. Looking at the mapped ride on my computer, it has me taking a few improbable shortcuts through the park - I'm assuming that this just a straight line connecting the dots from when the signal was lost to when the signal was regained. I'll have to dig a little, but does anyone know off-hand if there's some ride correction that you can perform?