[JKT]

Well I never, it works as it should with the all day unchecked... why doesn't it do this by default when you double-click the calendar area?

However, I'm not sure that this interface would work for OmniFocus as it is too cluttered. You can't have five boxes to click for date and time entry in OmniFocus as they wouldn't fit very well on a single line, and a substantial number of people don't bother with time entry. It might be better for the inspector though.