I don't have either camera or housing, but I too was impressed by the camera features. The earlier ZS3 is a great camera, so I would expect this to carry on. The only caveat, turn off GPS to extend battery life. The HD video and extra wide angle lens look to be great features.
The Panasonic housing is hard to find and expensive, but I have not heard anything much about it. The only suppliers I know of are in Japan and Malaysia. As with any housing, keep the O-rings clean and replace per the maker's recommendation. It's a good idea to buy a spare O-ring now, since it may be hard to get later. It's not going to be up to the durability of Ikelite's but these products only have a 1-2 year life anyway before obsolescence.
The Ikelite housing will be sturdier, and heavier. It's almost the same price as the Panasonic, so I would certainly consider it strongly if you don't mind the extra weight and bulk. If you can, handle one in an underwater camera store. It is possible to add a macro wet lens and a wide angle air dome to this housing if you want. The Ikelite housing lens port does block the internal flash, unlike the Panasonic housing's port. The cheaper Ikelite strobes are not much good for anything but macro, and since you optically couple to this camera anyway, you might want to look at Inon Z240 as a good match if you decide to spend the money for a strobe.
Those are my impressions. Let us know what you decide and how it works for you.
