I can give you a latest update.
I've had my 6 plus since the 22nd Oct, took some photos with it - but was mostly focused on the other parts of the phone. Well I started to look at my photos on the computer after I transferred them - and they were really terrible. My previous iphones were much better.
One day I was taking a video of my kid on a swing, and when I moved I saw the live image wobbling ! And the recorded video also showed it.
Then I was now paying more attention to when I was taking a photo. Basically if i would hold the phone really steady then open the camera app I could focus and take an ok photo, but once I physically moved the phone then it would go out of focus and it could not be recovered, until I would close the app and once again hold the phone steady.
Anyway yesterday I contacted apple support online, they ran a diagnostic test, said that the springboard is running out of application memory. So I backed up my phone and restored it as new. All this time the online support was patiently waiting for me, well having it restored did not fix the issue.
Right after that they setup a genius appointment for me.
This morning I had my appointment, and I was easily able to show the guy the issue/s. He said that he has seen this twice before. Basically something is wrong mechanically with the OIS system.
They had a new replacement ready for me, which I quickly tested in the store.
I went home, had to update from 8.0 to the newly released 8.1.1 software, then after that I was able to restore my backup onto the phone.
Point being I can now take good photos/videos with my phone again. Advantage of the apple store for warranty is nice to have.
Anyway if you have a 6 plus, keep an eye on it. As it has some physical motor/mechanism for the camera it may be bad, or may go bad.
I have not looked in depth at my photos for the other reported overprocessing NR, but I'm sure it probably still remains.