I just got back from a week of diving with my new g10 and OEM housing. www.seamusphotography.com/Utila2009
I don't think anybody makes a wide angle for this housing. If you find one I'd love to know about it.
You can't beat this housing for the price, but I do have a couple of complaints. There isn't a control knob for the thumb wheel on the back of the camera. It makes it tough to adjust in shutter or aperature priority mode. I haven't figured out a work around yet.
The housing seems to add quite a bit of lag time to the shutter release. I think this is because the connection flexes, so it is not so much lag time as having to push down hard on the shutter release.
Compared to my other canon housing(sd700), this one is very large relative to the camera. Which means it is very buoyant. I like my housing to be just slightly buoyant so that if I drop it overboard it doesn't drop to the bottom. Canon makes some weights for this which I'm planning to buy.
All in all I'm happy with the housing, but it has its limitations. I haven't used the other housings, so I can't comment on them