I've had a Canon G10 and it was great but I found the waterproof housing quite cumbersome to use. I used it a lot up here for a few years and even with care, corrosion got to the magnesium bits and I had some problems with the shutter button sticking. But it has lots of features and is very easy to use.
I bought a Canon 7D and it is exceptional, probably the best camera I have ever used, but you have to get good lenses to get the best out of it. I would highly recommend buying the body only and then investing in good quality lenses. Again, even though it lived in a bag inside a dry bag, the salt air has started making things a little tight and sticky. Mind you, I have taken about 35,000 photos with it over 3 years. The saltwater tropics are a harsh place!!! I will not be using it as often as I used to when in the boat, just to limit the exposure to the elements.
The HD video on the 7D is really good but you don't have autofocus, and I find it very hard to change focus manually and still get it right because you are only able to view it on the LCD display on the back, not through the eyepiece. I have a lot of cool GT strike footage which is slightly blurry, because of this. Very annoying!
I have just bought an Olympus TG-1 to have in the boat for general photos and HD video - we used a cheaper Tough Olympus in Hawaii for underwater stuff and it was really good for both video and photos. The benefit with the TG-1 is that it is extremely weatherproof and can be used underwater up to 40ft. It has lots of menu features and can also have a wide angle or telephoto (zoom) lens attached, which is cool.
Time will tell!