Just came back from a week long camping trip to Olympic National Park with the Sony A7RII I received just a few days before my trip. I have been a Sony shooter through A100, A700, A900, A77, A99, A77II, A7R, and now A7RII. I have to say that this is by far the best Sony camera I owned. I took lots of Milky Way images at 3200 ISO, none of them really needs much noise reduction. I will post some images later.
Back at home, I wanted to do a quick test to see with my own eyes how bad is the highly publicized long exposure noise issue. I connected the camera with an USB cable to my computer, captured a series images with Sony Remote Camera Control software. For the test, I turned off long exposure noise reduction, kept lens cap on, and exposed 30 second per image.
Before I started, I took an image at 200 ISO as reference. Then, I shot continuously for 120 images at 3200 ISO. It took slightly over an hour, including a couple of seconds delay between images. When it is done, I shot 4 additional images at 200, 400, 800, and 1600 ISO respectively. All images were magnified to 100% and cropped in Photoshop.
Here is a comparison of the 1st (left) and 120th (right) image at 3200 ISO:
There was a noticeable increase in noise after an hour of shooting. But the noise characteristics were similar. Nothing like the ugly spots being publicized over internet. To see how much the noise has increased, I put the 1st 3200 ISO image (left) together against the 1600 ISO image (right) shot after the series:
The noise levels were nearly identical, and noise characteristics was again very similar. It tells me that the noise level increased by about one stop after an hour of none stop shooting.
At last, here are the 200 ISO images before and after the 120 image series:
Again, the noise level was increased somewhat (if you can see it). But the level was so low that it is really not meaningful in real life.