I had a new car that also came with a Sirius radio and 3 months free. I tried it, but found it often dropped out while driving through forested roads in my area. That made it annoying to listen to. I stopped using it.
One thing I've found with the subscription services is that their "stations" are too homogeneous. I mean, I like jazz and classical, but I can't listen to just one style within those genres for hours -- especially while driving. And if you've got unlimited data, then there are free online "FM" stations, including NPR. WFMT out of Chicago rarely disappoints.
And the threat of having to pay for it limited my interest in exploring it any further.
