Saw this question on the Walt Disney World Facebook Page:
"WOULD YOU RATHER ... be the first one to enter the Magic Kingdom in the morning or the last one to leave at night?"

We have never been the VERY first or the VERY last but we have been among both. Nighttime was awesome. With the park practically empty at 1am, we had some great character interaction. The gate to the stage in front of the castle was open with no CM around to tell us to stay off, and we had a fun time horsing around. That being said, nothing beats a sunny morning at the MK! Everything is bright and new, super clean and you have the whole day in front of you.