Hello Aaron,
I just received a Seacam for my 1D Mark II. I have just been getting used to setting it up and running it through it's paces on land. I plan to get in a pool in the next week or so for my first test shots with it.
So far I am overwhelmed with the quality and workmanship. My Mark II slipped into the housing right from the get go and all of the levers/controls lined up perfectly, as they should for this price range. But considering all of the engineering that had to go into the thing to make available all of the cameras controls, it is truly an amazing device. If you can swing it and are not in a hurry, save your $ and get a Seacam. As far as service goes I can't say enough about the responsiveness of the folks at Seacam USA - Stephen Frink and Liz.
If you can get your 1Ds into the newer Mark II housing, it might be worth it. This would leave your options open for the future, incase you pick up a used 1Ds Mark II a few years down the road on ebay for $1000 :wink: You will be able to pop it into the housing. Also the new housing has an improved implementation of the * button actuator which sounds like a great way to use autofocus underwater.
Good luck with your search, Keith