Just bought one and did a road trip...
Took a weeks vacation (last week) and drove from San Jose, CA to Whistler B. C. , so I bought an XM radio (the Sony -- so I can use it at home, too).
Reception/sound quality were good (I'm using the cassette adapter), and I didn't have many interruptions (tunnels, some bridges, and in steep mountain ravine roads). I was surprised that there weren't any more interruptions from the mountains while in Whistler. The interruptions were more common near mountains the further north I went...
The Sony XM radio's interface is sorta cluncky, but I got used to it - could use more than 5 pre-sets for the 100 channels). And, it takes a second or two for a station to begin playing once a channel has been selected.....
Still finding interesting stations, tho... My favorite station so far would have to be the first (of the three) comedy station.