My friend on facebook with a Infiniti M said to try it since it worked for him.
I called and told the person about the offer and had XM on my car in 10 minutes from start to finish. Just have to pass them your XM ID number on channel 0 and a credit card, and you're done.
Worth it in my opinion since I'm too lazy to update songs on my iPhone and tired of the played out shizzle on regular radio.
It's $4/month with this deal, normally $13/month. Just cancel before the 5 months is up if you don't want to pay for a subscription after ($77/year with a deal).