There's been some discussion of the SPOT on the AOPA Forums. I haven't
read the threads, but see
http://forums.aopa.org/search.php?searchid=1976826 for a few of them.
I took a SPOT along on a trip to Alaska this summer with a friend in his
homebuilt plane. It worked great in the auto mode, posting our position
every 10 minutes to a web site where family and friends could track our
progress. After the trip I got many comments about how much the folks
liked being able to see where we were. I sent an explicit Ok message a
few times, and it was transmitted and the proper people contacted. We
went as far north and west as Fairbanks and Nome, and it worked fine
even at those extremes. Experiments at home in Oregon, though, indicate
that it needs a pretty clear shot at the sky. So it might not help you
out as an emergency locator if you were in a valley in mountainous
country, for example and couldn't get to a better place. But if you use
the auto mode, at least the last good position would have been recorded.
Our trip lasted about a month, and the unit was on in its auto mode
whenever the plane was in the air and often when it was on the ground
waiting for weather to clear, etc. And there's still a fair amount of
energy left in the one set of lithium batteries we used.
I feel I got more than my money's worth out of it, and highly recommend it.
Roy Lewallen