I have the regular Motion X (not Drive), bought it mostly to record my mountain bike rides and to use as an odometer/bike computer. I have an iphone 3gs and have issues with getting an accurate track and accurate distance/speed data real time. Even though I have GPS coverage at all times, the track will show no speed/distance intermittently (mostly after stopping then starting or changing direction) even though I am pedaling right along. I am not losing a signal. On my 6 mile loop that I ride, it may record 5.1 miles or so. It seems to lose a connection with the internal GPS whenever I turn sharp or stop and start. The recorded track shows the general shape of the loop but it is not representative totally (lots of cut corners, etc) Talking with the Motion X programmers, who are very helpful, they blame my phone, since the app depends entirely on the GPS chipset to work. Fair enough, I took my phone to my phone tech and the GPS chip checks out ok. He says the 3gs does not have a sophisticated enough GPS chipset to really record good great track details and accurate distances when it comes to mountain biking, etc. I have played with it for two weeks now and just can't get a good result with this app for my intended purposes. It records a track good in the truck where speed remains constant and there are not a lot of direction changes. I have the phone in a holder on my bars, and I know it is not losing a signal. I guess I need to upgrade to a iphone 4 for this app to work right. Any other 3gs users out there?