One of the best possible responses in various levels of conversation. There are many uses.
1. If you aren't paying attention to an elongated conversation and are struck out of your trance-like state of boredom to realize it's your turn to speak.
2. If you are put on the spot to give your opinion of something you don't particularly like or dislike, but you don't want to sound rude.
3. If you are trying to squirm your way out of awkward small-talk with someone you don't want to listen to.
1. Stacy: "...and then after he gave me flowers, he tried to KISS me! Eww!"
Rebecca: "...Huh? Oh. Interesting."
2. Joe: "So, how do you like the veggie burgers I made?"
Steve: "Well, they're interesting..."
3. Acquaintance: "Yeah, so how about them Yankees? I got their logo tattooed on my back last week. It's not healing properly though, the edges have pus."