XM, although not a necessity, is awesome. For $10-13/month, I really like having it.
XM isn't necessary for cross country driving if you're concerned about FM reception. When I drove from VA to AZ, the only place where I didn't get an FM signal was for about 100 miles across NM. The station I was listening to finally faded out. So I hit scan to find another one. Well, it kept on going, on and on! It didn't find one single station to get a signal off of. I left it on scan. Nearly 100 miles later, I finally got a faint signal that locked on.
I think the best part of XM is
MOST of their music channels are commercial free. They advertise commercial free music. So I subscribe thinking I'll never hear a commercial again. Man was I wrong! The ad did say "commercial free
music" after all. All of their news/talk channels and the comedy channels have tons and tons of commercials. I think the only commercials I've heard on their music channels are for their own service. And, the 80s and 90s channels have a DJ that does an awful lot of talking during the early evening. He even takes on-air callers! Play the freakin' music already!
When my wife gets home, I'll snap a pic of the XM install in our Escape. It's not hardwired in, but it'll give you an idea of a way to go.