Hey Dave, I don't know about the Sirius radio too much but I do have XM in my H2 and love it. To date I've had no problems with it and it seems that they keep adding more and more to the lineup.
I don't know if you have already, but if you go onto the XM website, you can sign up for their emails that alert you to new programs, stations and specials that will be aired! Just thought I'd throw that one at you if you hadn't already.
Take care,
BIMMEUP
Matt