Focus Numerique (translation here) published the detailed A99 ISO test. You can compare the A99 vs Nikon D600 comparison images here:
ISO 100: A99 vs D600
ISO 200: A99 vs D600
ISO 400: A99 vs D600
ISO 800: A99 vs D600
ISO 1600: A99 vs D600
ISO 3200: A99 vs D600
ISO 6400: A99 vs D600
ISO 12800: A99 vs D600
ISO 25600: A99 vs D600
As we learned from other tests take those comparisons with a grain of salt. But there looks to be a different noise handling between the two cameras. The A99 is a bit more aggressive while the Nikon seems to retain a tiny bit more of detail. What are your thoughts?
More reviews:
RX1 hands.on pics by Photographybay.
First day with sony alpha slt-a99v at RodKar.
16-50mm pancake test by John on Flickr.
Rokinon 8mm for NEX review at SonyAlphaLab.