99.9% of the time, when someone opens the calendar control and selects a start date, the next thing they want to select is the end date. SiteCatalyst keeps the focus on the Start Date form, and even if the End Date box gets highlighted, will periodically change the focus back to the Start Date as the user navigates through the calendars to get to the End Date. This is a little thing, but it would be a very nice convenience to have SC automatically change the focus to the End Date as soon as a Start Date is selected.
It's possible there is a competing, widely used, free platform that already works this way. For those users who use both, there are regular micro-moments of irritiation with Adobe for the way the SC calendar control works.