We had a Canon u/w housing for our A610 until the A610 brok (completely unrelated to the housing) so I've since replaced it with the A720 and it's matching housing.
The u/w housings definitely making the cameras more bulky but we do quite a bit of snorkeling on our vacations so for us it's worth the investment. I've considered buying the Olympus 1030SW since it's waterproof but I've read cases where they haven't been waterproof to peoples unpleasant surprise, not something I want to take a chance with so as long as I keep reading about cases like this I'll stick with the u/w housing.
You do have to be careful with the housings, we always rinse it off with fresh water after using it in salt water for the day and it's important to keep the o-ring greased and free of dirt and such. It's really not that difficult though.