Bummer about the Tracking access. I'm not sure what good the SPOT group think that service would be for anyone given the current access restrictions.
The Globalstar sat's are in geosynchronous orbits and if you look on their coverage map you will see that they certainly don't cover the globe. I believe I read somewhere that they are launching new sat's over the next two years that should help reliability and coverage. They are almost giving their phones and service plans away if you buy now with the expectation that it will work better three or four years from now.
As for the ability to send a message, I expect you will need "open sky" to get a good message out since they use the sideband services which I think are rather low power - although somewhat more reliable then their voice services.
I also have a concern about the GPS chip set being used in the SPOT. If it isn't one of the newer more sensitive variety like the SiRF StarIII, I think it will have the same issues with location lock as with the poor message transmission - SPOTty at best ...couldn't resist