I'm going to disagree w/ BluPhant on the Sirius vs. XM issue.
I *had* XM from July 'til November of last year. I thought that it was night and day compared to FM radio, but I thought that the programming was "strange". Here's an example: When you're listening to one of the Decades channels, for example the 90's on 9, they'll go from something like Nirvanna then immediately play a Celine Dion song. Now, granted, they were both released during the 90's.. but COME ON!! Given the right situation, I can groove to either, but back to back? Also, it seemed that on some of the other genre channels they merely put their collection on "random", rather than gave it any thought as to how the songs would flow.
Again, this solution was AWESOME in comparison to FM radio. So, if you only ever experience XM, you'll be pig-in-$hit happy with it.
However, what ruined it for me was when the guy I commute with bought a new Audi. It came with a free year's subscription to Sirius. To me, it was another great leap in listening pleasure. The songs would flow together. I knew then I would have to dump XM in favor of Sirius.
For me it breaks down like this:
XM Pros:
1. Cooler equipment.
2. Cheaper monthly subscription. ($10)
3. More subscribers, possibly more likely to succeed?
4. Dedicated (not shared) traffic channels.
XM Cons:
1. Screwy programming
2. Only two satellites (What happens when one takes a dump?)
3. Want to stream @ your computer? It'll cost you extra.
Sirius Pros:
1. MUCH better programming (to my taste)
2. Streaming @ your computer is free.
3. NFL while on the road.
4. Three Satellites.
5. Try before you buy.
Sirius Cons:
1. More expensive per month for basic subscription ($13)
2. Chunkier receivers.
3. Shared traffic channels. (Why do I care what's going on in Baltimore when I'm trying to get DC traffic?)
The bottom line is an agreement with BluPhant: *EITHER* Satellite radio service is worth the money. You'll realize how much you hate FM once you make the leap. With Sirius, you can try the service via streaming on your computer for free for three days. (If you've got more than one email address, you could conceivably "try" it @ your computer for as long as you like, making a change every three days..

) XM doesn't offer this.
Hope that this helps.
- Jeff