The quality of the music available via internet raido is much better than what is generally avaiable on FM, however the sound quality of good FM is much better (IMO) than what I've listened to on the SB. But some of them are not too bad. Obviously the higher bit rate stations are going to sound the best but the huge variety makes up for the lower sound quality, at least for me.
The biggest problem with internet radio on the SB is that I keeping finding new music to buy and it's costing me money.