Are you sure it's not the cooler calibration they chose this time around? My M9 is really bright with max brightness and auto turned off. I don't have my M8 anymore, but I don't remember it being any brighter. The auto brightness does seem a bit more aggressive this time around though. Have you done the comparison with auto brightness turned off?
ok, I tried this tonight and wow, it made a huge difference. with the auto brightness off, I can't see much of a difference. I like my phone brighter, so I am glad I put this out there. Thanks again msm0511