This is a great series of posts. People asked why Olympus, vs Nikon or Canon? Does Olympus have the support? The answer is they are all great camera systems, with good support. I am a long time user of Nikon topside and Olympus P+S underwater. I don't think there is an obvious right choice. It depends on what's important to you. But I'll offer my thoughts.
What about reliability? Olympus always have been well regarded in underwater P+S housings, from the revolutionary C5050 of 2002 to the current FE-360, which is the current best low end P+S on the market. Personally I've used Olympus P+S for years down to 40 meters and a little lower and never had a leak. Olympus has a lot of experience in making systems for underwater, and the PT-E06 seems to distill that into a great housing design. Nothing is perfect, but I'm confident that the PT-E06 will be a reliable housing at recreational diving depths.
What about cost? An Olympus system seems to be lower priced initially, by say 10-20%. However, when you look at a complete system over its life cycle, the cost advantage of Olympus is reduced. Olympus 4/3 system lenses are good but expensive, for instance. Trade in value for used Olympus gear is lower than for Canon or Nikon, in my experience. The net cost advantage of a system might be 10-20% if you buy new today, but the long term system cost might be similar to Nikon or Canon. So, I'm not seeing a great cost advantage long term.
If you already prefer Nikon or Canon, and have an investment in them, it makes sense to go with them underwater. Personally, I am very impressed with the reviews of the Nikon D90 with Tokina 10-17mm combo for underwater, and I already use the D90 topside with an array of lenses. You'd think I would automatically prefer Nikon.
But -- the compact size of the Olympus housing is very attractive to me. Size matters! I dive in Asia and have to carry the gear, and the size of a big Nikon outfit is daunting to me, both in the airplane and underwater. I've seen plenty of divers with jumbo systems in my travels, with gear from all over the world. They often got great results, but I did not envy them carrying that load around. So as a traveler, the Olympus system looks good to me.
I do have some concerns about possibly slower focus speed vs Nikon D90. Honestly the D90 is amazingly fast in that regard. I love it. But I generally use a focus light underwater, so I really wonder if that is an issue. I think not, based on other comments above. I think I will go with the Olympus system, and see how it goes.
