I use XM radio, the other service is Sirius which I cannot comment on. (no connection to the company etc.) I have it in my car. Its great even though the earlier versions are not that easy to switch channels and surf the 100 channels. There is a delay as the unit loads the digital stream coming off the sattelite of a couple seconds so its not exactly like button pushing on a radio. Newer units may access the channels faster. The other great thing is that you can see the name of the song and artist on the display which makes listening for new music and locating new artists, which I like to do, very easy. I have one of the early Sony movable units so that I can move it to my RV also. I am installing one on my boat that is a black box that hooks into the automotive CD player in the pilothouse which is Sattelite ready, very common now. I will also have to install an external antenae. I see that they now have units just over a 100 dollars that will play through an existing CD player that is not Sattelite ready and have a small portable antenae that you presumably hang out a window. Like a portable CD player that plays through the casette deck I believe. Like GPS the antenae must be visible to or see the southern sky. There are two sattelites for XM and they have coverage maps on the website. I think in some cities there are local broadcasts that cover when the antenae cannot see the sattelite because of the high buildings. In other areas, if you go under a shadow like a building, overpass, thick tree cover, or mountains, the signal drops off, can be annoying. There is some buffering in the units but not a lot. So you will have no signal in some areas where you cruise close to mountains that cover the southern sky to a height that the signal is blocked. Deep Fjords and being close to mountain ranges are where this may occur. I can see some anchorages being favored because of their view of the southern sky. Not a problem in open water. The coverage map seems to stop in Southeast Alaska but it extends beyond the coast. I really like the unit in my car and I now do not listen to regular radio except local news. Its that good. The music channels are great and the fidelity is excellent. I get the audio for FOX, CNN and MSNBC in my car. There is a monthly fee but I find that I get more use from this service than the cable tv that I shell out for each month. My thoughts are ..how long will the broadcasts be commercial free? I think some of the channels do have advertisement. I am a big fan of country music and they have about four channels which play continuous and have special programming where they interview musicians. I get a kick out of the truck drivers that call in from the road and make requests for songs..they all have nicknames. Like Road dog or Sneaky Peet or such...How come boaters don't have nicknames ...good buddy? John Kiapoko Krogen 48 Northsea Northern Cal