Google Play Music has added free radio.
http://officialandroid.blogspot.com/...supported.html
They acquired Songza and had those guys build it, but they've basically stitched it together with a Pandora/Slacker style system.
I used one of the Songza-style stations yesterday and it was decent. They have hundreds of them.
This morning I did a Pandora/Slacker-style song request and the station it played has been a string of good songs that I've never heard. I'm up to 12 songs and haven't skipped a single one, and I've wanted to download at least half of them.