Guys,
Wow, what a curve this thread has taken! I've played with the Olympus E300 and it certainly is cool.....Plus the price is right for many just starting out wanting more than a mid-range, shutter lag camera might be able to produce....
If Ikelite has enough demand for Nikon D2X housings I'm sure they'll make one.....As for the EOS 1DS MKII and other 1D cameras.....Beautiful to gaze upon, wax on about capability but no thanks....Far too much cost and weight to lug around. If Jim Watt and others can make printable and publishable photos with Canon's D60 (and now likely EOS 20D), plus Alex and me with a Nikon D100 I think a lot of this simply throwing $$$$ away. I've even used a Digital Rebel (!!!!!) and am on track to sell photos taken with my Canon G6!!! Computer post processing is a wondeful thing 
As James points out you can also upgrade somewhat easier with lower cost cameras if you choose a housing that doesn't require a second mortgage, Ikelite of course in my biased opinion 
IMHO if someone wants "the best" whatever that is and is willing to spend the $$$$ so be it...I think most underwater photography enthusiasts wrestle with the total cost of a Nikon D70, Digital Rebel or EOS 20D, etc. by the time you add up housing, ports, cords, strobes, etc. So new options like the Olmpus E300 might keep people interested in creating UW photos that feed all our souls.........
Sorry about the second rant (after Karl Dietz's comments, who's web site looks like he has a family to help support, too
but any hobbyist who spends $10-$15K +++ to make underwater photos of stuff already shot to death I think is a little koo-koo 
So in summary I think the Olympus might be another good choice once I see some tests on low light capability, etc....
YMMV
David Haas
Founder - PUPHU (Plastic Underwater P{hotography Housing Users 