I'm still trying to figure out what I want to do for an UW SLR system. I have a fairly large (~$12,000) investment in Canon lenses so I was (initially) under the assumption that I would be shooting Canon UW. However after deciding which lenses I would want to shoot UW (none of which I currently own) and deciding that I would be buying a new camera body for the underwater system, it has opened up the _possibility_ of switching brands for the UW system. At first I looked at the Olympus E620 with PT-E06 housing but I will be shooting macro most of the time and I want the Inon 45 degree viewfinder which is not supported with the Olympus PT-E0X housings.
Following the advice of the experts here of first choosing the lenses you want to shoot, recently it has become apparent that the lens I would really like to shoot with UW is the Nikon 105mm VR macro lens. The Nikon 105mm VR paired with a D90 camera seems to be a pretty compelling system for a reasonable price. Now if I can find a reasonably priced housing system for the D90 that supports the 45 degree view finder.....
I already shoot a different camera system UW (tetra 5050) and I have no issues going back and forth between it and my Canon SLR system so I don't _think_ I will have a problem switching between Canon above water and Nikon underwater.
I was wondering if anyone has contemplated doing this or if anyone is currently shooting both Canon and Nikon and what sort of advice they might provide?
PS: All my Canon buddies are like "Ewwwwwww". Of course their primary concern is probably if I were to go entirely to "the dark side" and they would lose free access to all my cool Canon lenses.