The only night time excursion I did, was a glass bottom boat tour. It was fun, although the fish weren't that colorful. The crew was great and the rum punch was plentiful. I did book it through the ship, and it was only a few dollars more than booking it right at the pier. But it did pick us up right at the ship.
I also went to the evening party at Snorkel Park. It was OK, but a much younger crowd.
The beauty of Bermuda is that you have so much time, there's not that fear of being late getting back...one of the main reasons people book excursion through the ship.
Of course the down side is that the shops and casino aren't open while you're in port. Some of the big gamblers found that to be a big disappointment!
Have never been on the summit, but loved the Solstice.