I purchased the "spot" GPS about a month ago and the next day had to drive to Tacoma, WA and had it track the journey in the car and it worked flawless. It tracked on google earth and showed the locations we stopped and also sent a signal every 10 minutes.
I then took it up to the cabin put it on the dashboard of the jeep and went out trailing with 5 jeeps. Snow wasn't all gone and had to cut 11 or 12 trees out of the way of the trail. And when we got back I checked the "spot" and it brought up most all of the locations. It will not show up if it doesn't see the satellite due to heavy forested area (where we were). (By the way we brought some "Tassani" or similar water with us so we wouldnt have to use the 911 button.
Went trailing again this last Saturday into some of the old mining trails with the "spot" and it worked fine as long as their was a clear shot to the satellite. In this area you will very rarely see another vehicle or person so it's a good investment. The other thing we do is inform somebody what area we are going to and if need be press a button on the spot that sends emails to whomever you designate and it will also send a pre-typed text message to whoever you want to send a message to.
Works fine and glad I got it.