I noticed an oddity in Rhythmbox Last.fm integration. Namely, when I load a radio station "similar to artist XX.YY" the player loads a list of ten songs, but from #6 to #10 they are a repetition of #1 to #5 in inversed order. Is it a problem with Rhythmbox?
This happens when you double-click the station to load the music selection, if you select it once and wait a second for the station to deliver the song queue, you'll only get them once. I have the same issue, and patience is the only work-around I've found.