My wife and I did this at 12:00 last night and actually did the whole experience as just a 2 piece, because there was absolutely no one else there and according to the staff, there hadn't been for a while... This may be because we chose a late slot or maybe because its not been very popular, who can say? I would say that I'm glad we did it by ourselves though, as we ended up 'completing' the experience and potentially wouldn't have with a couple of randomers. If you want the same result, try for a late booking.
Let me just say that my wife has NOT been a fan of the regular houses. She's done them all with me reluctantly, but she has been terrified throughout. As you sign the waiver for this thing, there was a staff member talking it through with us and she started physically shaking when he mentioned that we would not be together at certain points. In hindsight, I can see why they go through this with you, but it's definitely overkill in terms of the experiences overall intensity as whilst it's thrilling, it's not horror.
Ultimately, my wife loved it! As did I!
It made me feel like I was in my own private movie, where the consequences were real and we were in actual danger. The cast (lots of them) interactions were superb and the locations we went to were brilliant. I'm not gonna say much more than that, as you should really go into this thing fresh.
I'd say we were in and out in under 20 minutes, which you could definitely argue as being on the expensive side for $50 each. On the other hand, there are times in life when you have to treat yourself to a steak instead of a cheeseburger and as a HHN fan, I am so glad we experienced it!