How many Casts have you recorded where the presentation went 100% perfectly?!
Something that would really add value to Cast and make it more user friendly and less-time consuming is the ability to trim out sections/mistakes from your recording before it gets uploaded - not just at the start and the end of the full clip, but any snips from within the timeline.
It would be most intuitive if you can make a selection, delete that specific selection and the tool automatically snaps the remaining bits on either side back together (or even adds an automatic simple cross fade, or you could choose between a cross fade and hard jump cut).
I think the trim feature would complement the existing pause recording function nicely and make Cast a really functional tool that sticks.