I took a few High ISO 25600 photos with the Sony Nex-5n, and I think it did a pretty good job overall. There is definitely a lot of noise, but it retains detail a lot better than I expected.
The first image is a shot of my laptop taking with the Nex-5n and the 18-55mm Kit lens at ISO 25600. I also included an ISO 3200 of the same shot for easy comparison 😉 I aslo shot the image in Raw and applied the Adobe Raw Lens profile in Lightroom 3, That helped a bit with the Chromatic Aberrations on the edges, but nothing as far as noise in concerned.
Grilled up some steaks and it was really dark over by the grill. I set the Sony Nex-5n to ISO 25600 and fired away!! I had the Nex-5n in Best quality Jpeg mode for this image, so there is a bit of in-camera noise reduction applied that results in some jpeg artifacts. It can be seen in the 100% crop, but is really not to bad at all IMO.