It's interesting about the blackout walls. I can totally understand how many feel it's a "cop out", but there is another side to that coin.
I recently posted on another thread here about a year round haunt I experienced in the Niagara Falls area (Canada side) called Nightmares. There's actually a lot of year round haunts in this particular tourist area, but I had heard from multiple sources that this was the best one.
And you know what? It's essentially ALL blackout walls. No theming whatsoever, just near total darkness. (You find your way around by following a series of small red lights--which occasionally go out.) And that fear of the total unknown creates it's own fear. To a certain degree, that's part of the unease I felt in The Exorsist last year... those blackout wall sections were very disorienting, and you would really have no idea where the scareactors would come from.
So if used effectively, I have no problem with them. Fear of the dark is a real thing for many people.