I have an Ikelite housing for a Canon A640. It's been down to about 40m (rated at 60m) and so far (fingers crossed and touching wood) no leaks.
It's a bit bulky compared to the canon housing but I wanted the extra depth rating and the ability to attach wet lenses.
The controls seem to mate up okay, but the handle / weight is too big & heavy.
I got mine from a camera shop in Singapore (
:.:..Oceanic Focus...Singapore's one stop underwater photography equipment...Underwater Strobe, Underwater housing, Inon, Canon, Olympus, Nikon, Ikelite, You name it!!.... ) and even with shipping costs to the Middle East, it was cheaper than buying in UK. They also had everything that I wanted (strobe & lenses) in stock. Prices are in Sing $ and GBP1 = approx S $ 2.7
Personaly I would be wary about buying 2nd hand unles I knew the perosn selling, or it was a reputable shop.
Some of the compact cameras give superb shots and you can get some very attractive package deals, especially if you look at a slightly older or superceded model.
Cheers, John