Nice deal, great find OP!
For those that join, just call the contract termination team at Sirius/XM and keep asking to not be a customer. Don't take the first deal (be patient) and they will generally offer a great deal like a year extension for ~$50 or less.
Made me chuckle when we got a letter from them toward the end of my wife's contract. it had the following (I kid you not)
90 days: ~$50
180 days: $110
1 year: $80
Seriously!? Who would sign-up for 6 months for more than a year!?
Needless to say, I just called and we got another year for about $50 before taxes. For me, it is totally worth ~$5/month for all the great music you get.
They need to really get with it and offer multiple radio deals/packages. You get like a paltry 15% discount, or something, off the 'full price' if you have two different cars and want it to work in both. I don't know why they don't push this more and offer packages for 2-4 devices. That would be a great way to connect all your cars and maybe even a portable radio module connected to a home stereo, etc.