Why do you not use dSLR?

Less money, less worry. In a small bag I can carry two point 'n shoot cameras, 2 housings, a wide angle lens, strobe and arms. It's especially handy when I'm doing other activities during my vacation. Not buying a DSLR rig has enabled me to max out my 401k plan, add to my Roth IRA and put in additional savings.

I do a lot of diving from day boats (never been on a liveaboard). The smaller rig does less to put off other divers who might otherwise expect photographers to hog the animal encounters.

My future wife will hopefully be a doctor, preferably ortho/spine.

...

Live view: As far as I know, no DSLR has implemented a truly useful (for underwater photography) live view since the Oly E330 and now some recent Oly and Panasonic offerings for which there are no housings. Maybe I am wrong, but I don't believe the live view on the D90 and D300 are suitable for general underwater use. Please correct me if I am wrong here.

Referring only to the LiveView part, the new Sony DSLRs have a very similar implementation to the Oly E330, second sensor up in the viewfinder tunnel for a true "no extra mirror action" liveview, they just do it by having an optional tilt on secondary mirror (illuminate optical viewfinder or secondary sensor) while the E330 did it with a partially silvered secondary mirror. So they have the 'same' function but without the loss of light to the OVF when live-view is not in use. Otherwise I think I'd be in agreement with you that the Canikon liveview implementations are really more intended for 'tripod macro' or extremely wide DOF (no need for sharp focus) use.

I think from my readings that Panasonic is getting pretty close with single-sensor solutions and a fast electronic viewfinder that doesn't suffer much 'video lag' (at least their autofocus speed with liveview is getting a bit higher marks than Oly's EP1, in my readings) but not necessarily on all existing 4:3rd's lenses. Still the whole m4:3 family is still so new, there's a lot of room for improvement to happen very quickly.

I'm still hoping for a true Olympus successor to the E330 with a "Live View A" mode that works with all the original 4:3rd's lenses, but I'm no longer holding my breath expecting it. More than likely I'll be taking a serious look at a future m4:3 camera.....or outgrowing liveview and learning to use an OVF. Either will hurt, but the former would hurt the pocketbook (lens replacement in addition to camera/housing replacement, and high end m4:3 camera costs aren't that different from the entry-level DSLR bodies in my price range) and the latter more my pride.

Earlier this year I went thru an exhaustive investigation of DSLR vs PS for my new UW camera system. In the end I chose a Canon G10 with FIX housing. The deciding factors were:

Cost: Almost $10,000 for SLR system I wanted (Canon 50D, S&S housing, ports, lenses, strobes, 45deg viewfinder, etc etc) vs $2500 for Canon G10, FIX housing, macro adapter, YS-110A strobe

Flexibility: With the G10 I can shoot supermacro to moderate WA on the same dive and also shoot video.

Travel: With the G10/FIX systems (my wife also got a G10/FIX) we are able to pack both housings, cameras, strobe arms, 3 strobes, FIX fisheye dome port, batteries, chargers, macro adapters, and spare parts into one carry on bag.

UW Photos from Cozumel with the new G10 system: http://www.onewolf.org/Album/09Cozumel/UnderWater/index.html

Too heavy given today's airline bag & weight policies. Do all my diving travel diving.

The Nikon D90 does have live view!

Too big and too pricey

My wife and I shot weddings with medium format gear. I know the differences and all the reasons bigger is better in film and file sizes (sometimes) but it is really nice to pack the g10, and Fix housing, 2 ys 110's, and the assorted arms into a laptop backback and carry it on. If I use a small laptop it goes in as well.

I know I'll never sell anything and I do this for my own enjoyment. The limitations are from the operator and not the equipment in my case.

I need to remember the same things underwater as in the church--- Fill the frame and facial expressions make the picture. There is no facial expression on a fish's tail.

We chased technology for a bit and found there is no catching up so the g10 will be "it" for a while. Reasonable shutter lag, reasonably sized files. I'd trade the big files for less noise but I own it so it works. The focus is petty good but adding a focus light makes it great

jim