We spent the night in 2010 and loved it. We had the place to ourselves (except for surface support) which was a nice benefit.
One of the pods has two bedrooms that can sleep up to 3 people in each; the center of the habitat is the wet room with gear storage and moon door access; the other pod has a kitchenette loaded with snacks and an entertainment area (and what movie is more fitting during your night underwater than The Abyss?!). It was fun to look out the windows and see lobster crawling around the edges and fish swimming by.
There was a bit of an algae bloom when we were there, so viz wasn't the best, but we still had a great time. We did 5 excursion dives during our stay (30 to 40 minutes each) which was plenty of time to explore the lagoon. Each excursion made us feel like we were astronauts - notify surface support that you are leaving, gear up, and slide through the moon door in the floor and find yourself in 30 feet of water - when the dive is done, simply swim back up into the habitat.
Truly a unique experience and one that I would recommend to others!