Ive purchased the QC 35II just a few days ago and have yet found a way to make everything work as expected at once.
Im using it on a windows 7 OS with bluetooth.
In the beginning I thought there was a white noise problem, so I updated the firmware to 4.3.something. The white noise problem was gone but I couldnt use the microphone anymore (windows just didnt find it anymore and when I took it off the bluetooth list and reconnected it , it said 'microphone cant be used' after it showed the dialouge that the headphones were connected now).
I looked for some fix and found a post here that said connecting them via USB and resetting the bluetooth list could work , so I did that . Well, it worked for the microphone but now I have the white noise problem again - turns out tho , it's more of a noice cancellation problem - as soon as the headphones get any audio input , the noice cancellation seems to just stop (and I can clearly here the AC/Air cleaner sounds that Im trying to block out using the headset ). When I turn off audio the noise cancellation will work again and I can hardly hear anything from my enviroment anymore.
Also , there is a considerable audio lag (3-10 seconds !) from time to time. It was there when I first set up the bluetooth connection to my PC and reappeared when I tried to fix the microphone. Now, it's there sometimes when I start spotify/windows media player/youtube and will randomly vanish after using in browser audio input like youtube.
All in all I love the QC35II when it works but unfortunately it hardly has really worked as intended yet.