I bought a big EWA marine SLR deep bag... I used $1500 worth of 35mm SLR gear in it at times... It worked quite well for the price... I'm sure it wasnt as nice as a real housing although it was a lot easier to rig up and maintain. I used it in the blue hole in belize down to about 147ft. The bag took about 30 dives... on that last one I noticed some small bubbles coming out of the bag at around 110ft.
Now, unlike rigid housings, the ocean will squeeze the air out of the bag decreasing its volume before it will begin to actuall fill the bag with water. The bag has a one way blow valve on it so you can inflate it yourself at depth. This meant I continued my dive for 5 more minutes before I surfaced slowly, taking a safety stop, and even though it had been leaking air for some 15 minutes no water got into the bag. EWA replaced the bag for free.
If given a choice between an EWA bag and a real housing, I'd of course choose the real housing because of the easier controls, especially if i had a digicam with hard to use controls, but I was on a budget.
The most annoying part of the EWA bag is caused by the same thing that makes it really really hard to flood: the variable volume. The EWA bag is a bouyancy PAIN IN THE ASS! It's not unmanagable, but it is annoying. If you have the money, get a real housing designed for your gear. If you don't have the money, get an EWA bag.