NextRadio lets you send feedback to stations telling them what you like and don't like.
From the Now Playing screen, swipe to the Recent screen. Tap the overflow (three dots) icon next to the song you want to like, dislike or buy. Then tap the option you want.
The Buy link takes you to the iTunes store where you can buy the song.
You can also share what you're listening to via text, email and more by tapping the Share icon.