While you're listening to a song, you can hit the "+" button to pull up options to see lyrics, the artist's bio, or create a new custom station based on that particular song. There are also links to buy some songs directly from Amazon MP3. If you don't like the song you're listening to, you get six skips per station. After you use them all up, you'll have to listen to songs in their entirety or switch over to a new station (which will replenish you with six more skips).
One bonus feature I love is iHeartRadio's Sleep Timer. From the settings menu, you can set the app to stop after anywhere from 15 minutes to 3 hours of playback.
While iHeartRadio is certainly impressive, it isn't perfect. I would love to see the app add some of the DVR-like features that TuneIn Radio Pro offers. I realize that adding these features might come at a price, but still, it would be nice to be able to pause, rewind, and record radio content for later playback.
Overall, iHeartRadio is the best completely free streaming radio app I've seen. It takes some of (but not all) the best features from TuneIn Radio Pro and combines them with Pandora-like functionality. The custom stations are ad-free, programming is top-notch, and the app is easy to use.