The existing killer app for WebRTC is video chat without installing an app, which is huge.
Other P2P uses are very cool and interesting as well - abusing it for fingerprinting is just that, abusing a user-positive feature and twisting it for identification, just like a million other browser features.
The technique doesn't actually rely on webrtc though, does it? Not showing up in the default view of chrome's network inspector obfuscates it a bit, but it's not like there aren't other ways to do what they're achieving here.
Other P2P uses are very cool and interesting as well - abusing it for fingerprinting is just that, abusing a user-positive feature and twisting it for identification, just like a million other browser features.