I have no way of knowing how popular it would be at night and I have to assume IOA and USF should start keeping longer hours, but based on my family I really think we would love the option to visit in the evening.
We are FL resident pass holders, but we live just far enough away that we stay in Orlando whenever we plan a trip to any of Orlando's attractions. My wife and I do not last too long at a water park, so I just see it as something we would do from say 7 PM to 10 PM if they offered a decent price admission for evening hours. Since Cabana opened, all of our stays have been on-site, our daughter is way too young for the bars and although we always have a car, I tend to like to park and leave the car. We enjoy the mini golf and the restaurants, but w/ more rooms coming-meaning more guest, the more options the better!