I've used the Sprint Navigation feature 3 times now. I've never had a GPS device before. The first time was from San Francisco to Menlo Park. It went smoothly; I missed my last turn and the GPS recalculated quickly, and it handled navigation in the business park's small parking lot. The second time was for a trip from San Francisco to South San Francisco to the FedEx distribution center. This was a shorter trip and the parking lot was much bigger than on the first trip, but it got me there in one piece.
Things did not go so smoothly on the third trip. I was going from San Francisco to San Bruno to an address I'm familiar with, but I wanted to use the Navigation to test it for this blog post. The Pre had trouble communicating with the GPS mothership while still parked in my garage. Instead of waiting I decided to just start driving and see if the Navigation would just catch up with me. Based on my other experiences, I didn't think this was an unreasonable expectation, but on the fifteen minute drive it only connected with the satellite once, and then it told me I was going north when in fact I was going south.
Later on in the day I was using Google Maps to search for a restaurant, and Google Maps was showing my location about 6 blocks away from my actual location. I think the problem may have been that I had turned off the GPS a few days before, then turned it back on some time later. I tried rebooting the phone and that seems to have cleared up the problem in both Google Maps and Sprint Navigation.
The two big problems with the Navigation are the battery drain, and the heat. The fifteen minute drive to San Bruno dropped the battery charge from around 50% to about 25%, and good grief that thing gets so hot that you can fry an egg on it. I hope this experience was not normal, due to the Pre constantly searching for the satellite. I'll have to do a follow up post at a later date. Accessories that seem very necessary are a car charger and one of those generic PDA/phone holders that slide into the vents so you can blast the A/C on the thing and keep it from getting unbearably hot.