I'm new to it as well. I got mine used figuring I only needed it when I was offshore out of the range of my standard VHF radio. This SSB radio will apparently, under optimal conditions, allow me to contact people several hundred miles away. Not that I need that much power but my VHF only goes about 22nm and I rarely will fish within that limit.
The radio allows acces to certain weather fax frequencies, emergencies and of course the coasties if needed where in many cases my VHF radio is limited. I can also talk from canyon to canyon with my fishing acquaintences in the event that they are doing better than myself and hence allow me to get in on the action.
I chose not to get a satillite phone because of the cost both initial, monthly and per use. I ccan apparently do a lot with this unit...most of which I don't understand yet. Hopefully with all the reading I'm doing this will clear things up.