Great discussion and an ideal candidate for the Best of Wetpixel.
For me a housing must have good ergonomics - so you can change settings quickly and efficiently underwater and get the shot. While I had my D100 I dove with lots of people with the same camera but different housings. And it was clear that housing ergonomics meant I was getting images that they weren't. Nothing to do with photographer skill.
The other important factor is a housing that is easy to live with. Easy to slide the camera in and out. To take topside shots between dives. Althernatively have a housing that allows you to download pix or change lenses without having to take the camera out of it.
Alex
