Selecting "I'm tired of this song" puts it on the shelf for a "period" of time. Apparently this period keeps changing and it seems to me that the more songs you put on the shelf the more quickly they come off the shelf. I'm at the point where 80 percent or more of the songs selected by this stations are songs which I put on the shelf, some of them recently. This is the station I've been grooming to help me discover new music and since I can't thumb down the songs to get them out of the way this is my only option. This feature would be much more useful if the user could configure how long shelved songs remain on the shelf. I would prefer the choice to include a never option so that songs on the shelf will remain there until I say otherwise. One size fits all means it actually fits few or none, so please make this option configurable.
Along the same lines (although of much less importance to me) it would be nice to view and perhaps edit songs on the shelf. This would address the concerns from other users that accidently shelved a song and had difficulties getting it to play.
I would even be alright if this enhanced functionality was only enabled with a paid account. As it sits today I spend a lot more time putting songs back on the shelf again and again than listening to new music, which was the only reason I joined. I have 6000 of my favs on my phone and various playlists to cover them - I do not need or want a service to play or manage these songs. I can listen to them on the go via earbuds or in the car via bluetooth, or at home via USB or Bluetooth.