James,
Here's my take on some of your criteria....(and you interupted me at 11:25 p.m. in Ohio as I was trying to design the logo for PUPHU (Plastic Underwater Photographers Housing Users 
Sorry in advance for the CAPS to seperate my responses....
1 Does the form follow the functions on the camera, or is it more of "We can fit that camera in our box?"
DON'T MATTER AS TOO TIGHT = FLOOD IN A SECOND.....PLUS USUALLY COSTS MORE FOR NO GOOD REASON OTHER THAN MAKING IT A LITTLE PRETTIER, maybe...
2 Is the way the camera is mounted well thought out - making the system easy to use?
AS I POSTED IN THE DSLR FORUM A SWISS ARMY KNIFE FLAT SCREWDRIVER BLADE IS ALL YOU NEED FOR LESS THAN 2 MINUTE ACCESS.
3 Does it require you to totally take everything apart to change the memory card?
NOT IF YOU HAVE A CANON DSLR....
WITH SIDE MOUNTED MEMORY CARD ACCESS...
4 Are the controls at your fingertips, even if that means there are a few more gears and shafts to transmit that force to the button or dial that matters?
MORE GEARS = MORE SET SCREWS AND THINGS TO COME LOOSE. USUALLY WHEN THE MAMA DOLPHIN IS NURSING HER CALF OR WHALE SHARK IS GIVING BIRTH RIGHT IN FRONT OF YOU...
5 Does the port selection let you use the lenses you own or want to use?
MANUFACTURERS USUALLY HAVE MORE OPTIONS THAN USERS WILL EVER USE. PLUS MOST UNDERWATER PHOTOGRAPHERS NEVER BOTHER TO MASTER ONE LENS BEFORE BUYING THE NEXT "GREAT THING".
6 Can you switch from manual to autofocus underwater?
OTHER THAN 100MM AND LONGER MACRO FOR PYGMY SEAHORSES , WHO USES MANUAL FOCUS?
IF YOU BUY THE RIGHT LENS (Canon 100mm macro with USM allowing manual overide focus anytime) this isn't a problem. AUTOFOCUS AS EVIDENCED BY KARL DIETZ, MYSELF AND OTHERS IS A BETTER TOOL IF YOU LEARN HOW TO USE IT THROUGH PRACTICE.
7 Is the viewfinder big and bright?
NO DSLR IS EVER GOING TO HAVE A VIEWFINDER LIKE THE OLD SPEEDFINDERS.....THE BEST YOU CAN HOPE FOR IS SOME MAGNIFICATION, THEN BUY YOURSELF A LOW PROFILE MASK AND SMASH YOUR FACE UP TO THE HOUSING BACK AND PULL THE TRIGGER...
8 Does the housing give you tennis-elbow when you are trying to shoot macro?
DEPENDS ON THE HOUSING BUOYANCY AND PORTS, PLUS INDIVIDUAL LENS CHOICE...
9 How is the customer service?
GENERALLY GOOD FOR MOST (EXCEPT MAYBE SEA AND SEA SUPPORTED BY TABATA USA NOW (TUSA, and I haven't heard or read any good or bad on their product service here in the USA.)
10 Is it easy to mount your strobe arms to the housing where you want them to go?
ALMOST ALL MOUNT ON THE HANDLE TOPS ALLOWING EASY AIMING OF LIGHT. (Anyone know of a housing without top handle mounting? Betcha' can't get your strobe light into a hole without top mounted strobes 
11 How easy does everything break down for packing?
WHO TAKES THEIR HOUSING COMPLETELY APART? MOST BASEPLATES COME OFF WITH A FEW BOLTS....MINE NEVER DOES AND DROPS IN A PELICAN 1620 ALONG WITH EVERYTHING ELSE EXCEPT PORTS AND CORDS STOWED SEPERATELY.
12 How long does it take to get the camera out of the housing to take a land photo?
TWO MINUTES MAX WITH MY TRUSTY SWISS ARMY KNIFE SCREWDRIVER BLADE 
13 Does the housing offer some kind of digital TTL circuitry?
RIGHT NOW ONLY IKELITE FOR DSLR CANON ETTL AND ETTL2 AND SOON NIKON D70'S ITTL . PLUS FUJI S2 STANDARD TTL...NO OTHER WORKING MODELS OUT THERE TO MY KNOWLEDGE....
Whew! I'm pooped and heading to ZZZZZZZZ.......
What fun 
David Haas
www.pbase.com/dhaas and www.ikelite.com "What's New" links....