In Playback mode, I would LOVE the ability to specify a date/time to begin (and optionally end). The slider/scrubber UI is infuriating when you’re trying to zero in on a specific time. Just let me select the time to jump to via normal input fields/widgets. For creating a clip to share, being able to specify the duration or end time would be nice too.
Also, allow the user to control the speed of playback (1X, 2X, 4X, 8X, 16X, and 1/4X, 1/2X, for example).
Oh and also web interface and multi-view in the app, please!