We have used kids night out 3 times and loved them. (multiple trips)
They show up with toys, read to the kids and play with them. If I had been in the room we would have been watching TV and they probably wouldn't have gone to sleep until 10 or 11. All three times DH and I have gotten back and they read and played games until going to sleep at 9-9:30.
They wake up the next morning rested and in a good mood to get to a park. I almost wish we could afford to just have them babysit for dinner every day.