Well, the Olympus OM-D E-M5 has been out for a little while now and has already received the full bells-and-whistles review from DPReview, so there's not too much point giving any technical background on the camera or listing all the headline features. My general take on the E-M5 is that this camera really is a wonderful example of the merging of electronics and technical wizardly with the traditional camera. I think that we're really starting to enjoy the fruits of the development that has occurred since Canon first put a CPU in the AE-1 and even more so since the digital sensor began to replace film.
In the last two years the way that I use cameras has changed dramatically; going from a viewfinder-based SLR style to live-view, tilting screens, waist-level shooting, chest-level shooting, ANY-level shooting. The E-M5 is a fine example of a camera that allows me to continue down that path. Ergonomics are an issue when a camera like the E-M5 is made to be so small (and it is small, don't let the DSLR look fool you), but this is another area that I have comes to terms with. Whereas I once would have said that an Olympus Pen was a bit awkward and the grip on a Panasonic G/GH too narrow, I've simply adapted, even if it means holding a camera in a completely different manner to what I was once familiar with.
You can still operate an E-M5 like any other camera, but the above grip is how I learned to love the Panasonic GH1, how I enjoy using the Canon G1X, and will also be my default grip for the E-M5 as well. The common feature between all thee three cameras I just mentioned is a tilt or articulated screen, a finger grip of sorts, and a front control wheel that can be operated with the forefinger.
My first usage of the E-M5 was at night after I had travelled into the city to pick it up. With some charge in the battery I immediately gave it a test run and knew that I had the first camera that I ever really enjoyed shooting at night with. Yes, the higher ISO performance is a big improvement on any Olympus before it, but ironically that was not the most impressive feature. It was the speed and accuracy of the AF in low light combined with the superb new "Five-Axis IBIS" system that really got my attention. Ray showed some examples using the IBIS in his "Month in New York" thread, and I'll add a couple more here
All three were taken handheld with a 25mm lens (50mm equiv on Micro 4/3). I feel that 1/3 second was acceptable limit to get genuinely sharp images assuming you were steadied. BTW, these were all taken at waist or chest level which is no less stable a way to hold a camera than the traditional eye-to-viewfinder IF done correctly.