I decided to do a little investigating to try and figure out what bitrate iTunes radio streams at. I closed all my applications except for iTunes and my resource monitor to track my network traffic. As I was streaming a song the incoming network traffic for iTunes peaks around 400 kB/s but then falls off sharply several seconds into the song. It's obvious that iTunes creates a buffer for the rest of the song as the song begins and then plays from the buffer after the entire song has been downloaded. From here i captured the total received bits during the playing of a single song and then calculated the kbps from there. I tested several different songs and most bit rates fell in the 280-300 kbps range. Now, not all of this data was strictly for the song being streamed since iTunes almost certainly has some overhead for simply running the service apart from song data. It seems to me that iTunes Radio is likely streaming at the full 256 kbps AAC format that they sell their songs in. FYI, I do have iTunes match so it's possible they reduce the quality for non match subscribers a la the Pandora premium service.