I've used the SPOT 1 for three seasons now.  Never had a problem.  Like IC mentioned, a couple times, I needed to move it near the shoreline to get it to link with the satellites.  I know it's sent the ok message when the 2 lights stop blinking together and only one blinks.  I'll use the "help" message only if I'm staying at the same site the next night due to weather or because it's a really nice location.  Haven't had to send an SOS message....knock on wood....it is fun to get home and see the track and campsites I used during the trip....