It would be neat if after a presentation, the speaker had a summary of the time spent on each slide
A summary of the time spent on each slide or each "chapter" seems like a feature that is easy to implement (just record the timer value upon slide change). This can help hone one's timings, and adjust the speaker notes accordingly, especially for presentations "in the wild" given multiple times. Actual timings are often very different than planned ones!! In the same vein, having a second, smaller timer and time limit per slide would be very useful. Thanks for the best slide software out there, by a long shot!!