When I bought Mobile XT for my HP iPAQ 910 (running WM 6.1), I already had been shopping for a GPS for my car for some time.  The list of features for this smartphone-based navigation system seemed to cover what I needed, and the price was certainly attractive.  So, I ordered one without any delusions that it would be as good as a dedicated unit like a Nuvi.  But, I have been pleasantly surprised. Just for the heck of it, I stuck the micro-SD card in my phone while I was sitting in the parking lot of the Post Office after picking up the package from Garmin, and within 3 minutes, the software was installed, the unit was tracking on 6 satellites, and my phone was telling me how to get to the service station with the cheapest gasoline in town.  I wish the screen was easier to read (a problem display size on my phone, not with the software), that I could copy the software to my 8GB micro-SD, that the voice directions included street names, but I have a very functional navigation system at a very reasonable price.  And I have one less piece of hardware to carry around.