I have Sirius, and it's a good service and a good company. Sirius worked with me, technically, when it came to diagnosing reception issues in my area. They even called up their special Panasonic hardware vendor support line with me on the phone to go over hardware issues (Which it turned out to be)
Sirius buys a lot of third party streams. Streams like the Vortex - Which is a stream you can get on winamp for free. So whatever ads the Streams may carry make it to your ears.
The cost was ok - Sirius gave me 4 months for free.
I'm using a Panasonic CR-SRT100 antenna amp box (That actually gets hot when it can't find a satellite) into a Panasonic head. The tree cover in my area (Tree tunnels in New England block the signal quite well) is the biggest problem.
I am using the Terk / Sirius low-profile antenna that was on display at SEMA this year. In my Civic hatch with no sunroof the signal strength is incredible. All in all, worth it especially if you travel.
There aren't great techno stations. Lots of house and dance, but no real techno (Orbital, BT, Chicane, Prodigy) and there is no good trip-hop (Hooverphonic, portishead, Si*Se).
Tons of Spanish channels. 3 childrens channels. Lots of really good news / weather / opinion channels.
A gay channel, which must come from the satellite of butt-love or something.
a huge country and rock section, and two really good 60's/70's underground stuff (Procol Harum, Cream, Rainbow, Blue Cheer) And a sports section that I have never listened to.
Oh, and 3 religious channels. Like I don't get enough god on the radio in the plains states.
All in all, a great travel companion, more worth it than EZPass... But I have an MP3 / WMA player too, which is like listening to a stream of YOUR favorites for 11 hours per disc. And after a while, I now have 7 discs full of my MP3 collection. So while it's nice, I'm not attached at the hip.
-> Steve