Actually, RDIO has never been forthright about what quality they stream in.

From their customer support in their knowledge-base:

-------- "We're not currently providing specific bitrate or codec information. We experiment with different rates and encoding formats in an effort to provide the best possible listening and user-experience, and stream CD-quality audio over the web and wifi (for mobile devices), and only stream a lower bitrate if you’re on a 3G connection.

We realize that is not be as much detail as you’d like, and we apologize for this — if you have feedback about Rdio’s sound quality as you're listening, please do let us know." --------

That's bitrate, which doesn't necessarily correlate to "sound quality". Vorbis at 160 kbps usually sounds better than MP3 at 192 kbps.

Okay but Spotify premium streams at 320kbps all ogg vorbis.