Rdio has spent a large part of 2012 revamping its mobile app, and a new beta shows that it's still full of ideas with two months left to go. The 2.3 test version makes the ubiquitous hidden sidebar even more unavoidable than we've seen before, but those not irked by UI homogeneity will be happy to see Rdio gain some multi-device harmony: along with syncing whatever's being played from desktop to mobile and
