Overall, it seemed to perform well, but I have a couple of suggestions for the designers.
Spot certainly kept track of my movements during the course of a river trip of 60-some miles down the Yampa and Green rivers. Triggering Spot's daily messages was easy enough. I turned on the bright orange transmitter and let it acquire all the satellites it could while I set up my tent. Then I pushed the "OK/check in" button to send word that all was fine and good.
And, as you might have noticed, all the messages got through.
But....the inability to construct email messages in the wilds can prove to be something of a problem. Proof of that is the fact that when I programmed my emails before leaving for the river I didn't know that there would be a layover day on the Yampa. It was a glorious day, one that allowed ample time to hike away from the river and explore some incredible settings.
However, those receiving my daily emails didn't know there was going to be a layover day and weren't quite sure what to make out of the fact that the coordinates sent on consecutive days were from the same location -- indeed, the transmitter on Tuesday was probably within a foot of where I had placed it for Monday's transmission.
A similar problem exists with SPOT's "Help" function. You can't alter the email message you put into the software before you left for your trip. As a result, you can't let friends and family know that, "Geez, this is such a beautiful place, I'm going to spend an extra day, so don't worry if I don't come home as scheduled."
Hopefully, future models of SPOT will address those short-comings.
That said, SPOT is a good tool for letting family and friends know your trip is progressing smoothly and, in the case of true emergency, will allow you to get word out that help is needed.