It's a good service idea, but the misconception is that it's commercial-free. There's actually something like 70 out of 100 stations that will have some advertising.
Other than that, though, if you have the hardware to receive it, it should be a cool service.
It uses 2 boeing 702 satellites in geostationary orbit whose names are "rock" and "roll". They are transmitted down to repeaters on the ground which should effectively make it possible to drive from NY to LA without ever losing the radio station you're listening to.