I would add that I think I can get an improved file from the Olympus using Raw and my own noise reduction settings and when I tried the NEX-5n at these high ISO settings I always found the jpgs. were cleaner. Make of that what you will. However there's no doubt in my own mind that the OM-D is a marked improvement on previous m4/3 cameras at these higher settings and that the Dpreview suggestion that this possibly is the best ever mirrorless camera, let alone m4/3 only, is not as far fetched as it might seem at first.
I would however finally like to point out that the NEX-5n is still a fine camera and when you take into account at what price you can buy it for currently, compared to the other two, then it shows just what great value it is.
N.B. to see more on the cameras and lenses featured in this post click on the relevant labels (tags and keywords) below.