In an emergency, there is something about actually being able to talk to someone, as opposed to pushing the button and hoping your message went thru. A call for help, whether to professionals or to a friend is more efficient when you can communicate details about the situation and the folks coming to help you know what to bring and what they are in for. On the other side of things, when I am the wife at home (as opposed to being along in the field) it is so great to get that quick call and now everything is alright, or even those calls where I find out Luke is weathered in or otherwise delayed someplace provide me peace of mind in knowing he is safe and I don't have to worry. Also, plans can change, and on fly out hunts its really handy to be able to talk to your transporter about early pick ups if we tag out early, or flight delays if the weather gets ugly.
The SPOTs do have a lot of potential, we carried a borrowed one (in addition to the iridium) on our 100+ mile backpacking and pack rafting trip and left it on each day to post our "tracks" to a website for family and friends to follow while we were out. Our folks reqlly enjoyed being able to track our progress each day of our 8 day trip. It transmitted every day of the trip except for one, a day in which we had pretty low ceilings and bad weather. Would have hated to rely on it for a real emergency though, as there are no guarantees and little confirmation.
To date our iridium phone has had to call the medevac chopper in twice (once when I fractured my leg on Kodiak, and once when Our bro-in-law's dad who borrowed it had a heart attack on a remote snowmachine trip) For us the sat phone has been money very well spent.