Megaixel.net also has good reviews of a lot of different cameras.
The Oly does seem to be the popular camera, but (I think) Dee said that the PT housing for the 4000 is being discontinued.
About shutter lag. I have an SLR, Minolta 7000 AF. Even with it, if I just raise the camera and push the button, it takes it a second to focus and release the shutter, so it's not really something I see as a drawback because I'm used to it pausing for a sec or 2. Now a manual focus SLR will drop the shutter the instant you press the release, but it may be in focus..maybe not. That's why the have the fieldgoal posts for the macro lenses. The focal lenght is set, you just frame the shot with the guides and hit it.
Again, I don't worry about shutter lag that much, I have a 512mb card, I just take picture after picture until I get the shot that I want, then move to the next object. It's still way cheaper than shooting a 24 shot roll to find 23 fish butts and 1 face out of focus.