I have had the Canon 5D Mk II and the S90 for quite a while, and have been happy with them. But recently I bought the Olympus micro 4/3 PL5 for my scuba diving. I actually like it quite a bit, and have been using it for traveling and underwater photography. The system is very light. I have the camera with kit lens, a tele, the Panasonic fish eye, the flash, filters and lens care kit all fit into a small compact carrying case that all together weighs no more than my D-SLR camera body. The Panasonic micro fish eye is an amazing little lens with great optics, and very fun to use on land and underwater. I also like the HDR bracketing of the Olympus PL5, there are multiple customizable settings. With Photomatrix, the HDR shots are amazing. I now use the Olympus most of the time, and take my D-SLR out for serious portraits and low light action shots. The fish eye and HDR function have given a fresh breath of creativity to my photos.
I got the Olympus instead of the Sony because it has a factory diving UW case that is well made and inexpensive. The kit lens is very compact and did well even 80 feet under water with my UW strobe. Its lenses are also more compact with a wider selection and better pricing than Sony. But if you do not do any underwater photography or do not care about costs, then Sony is fantastic.