1) Have an option for the "minute" slider to have 1 minute, 5 minute, 15 minute, and/or 30 minute resolution. For example, I am never going to have a 29 minute meeting - it will always be 15 or 30 minutes. So there is no need for the slider to have all those intermediate values. This would make data entry faster.

2) Even better, have 5/10/15/20/30/45/60 minute "meeting duration" buttons on the START TIME entry screen. So I can click on "start time", select the start time, click "20 minutes", and add a 20 minute meeting starting at that time. It's faster than having to enter both a start and end time. 99% of my scheduled items are 5, 10, 15, 20, 30, 45, or 60 minutes in duration. Perhaps yours are too?

3) Have buttons next to the start time entry field: "After last meeting", "15 minutes after last meeting", "30 minutes after last meeting", "45 minutes after last meeting", "1 hour after last meeting". When scheduling multiple items, I frequently schedule them consecutively (or, I'll add a 15 minute break, a 30 minute lunch, or a 60 minute trip to the store between tasks). This would make data entry even faster!