There's still a killer feature which is only just now (autumn 2016) being slowly supported by HTML5, and this only for some browsers: Client side video recording and streaming to server. Another one is peer-to-peer. WebRTC is more complicated than RTMFP and still not implemented for all browsers.
We have started to develop a replacement for our Flash app and are fighting a lot with specified but not yet implemented features. Especially configuring the webcam (resolution, frame rate) is still in a very sad state of implementation.
Ah, I hadn't heard about that API. But audio/video encoding and streaming was a basic use case from launch. I guess the new API lets you handle the encoded data yourself, and not necessarily send it out over WebRTC.
MediaRecorder is essential for video encoding. A friend of me had to implement video encoding in JavaScript when he tried out uploading videos to the server. He did something like this: write a video frame to a canvas element, then encode it in JPG and upload that JPG to the server and then make a video out of the JPG frames. Absolutely ludicrous.
We have started to develop a replacement for our Flash app and are fighting a lot with specified but not yet implemented features. Especially configuring the webcam (resolution, frame rate) is still in a very sad state of implementation.
An example is MediaTrackCapabilities: https://bugs.chromium.org/p/webrtc/issues/detail?id=4807 and on MDN you get Not Found: https://developer.mozilla.org/en-US/docs/Web/API/MediaTrackC...
In short, if you try to implement this: here be dragons! while this is working in Flash for years.