I am sure many of us are experiencing the annoying auto brightness bug on our Nexus 7 that got introduced with version 4.2. Please go to the link below and vote for this issue (star it), as it doesn't seem to be on Google's radar right now more votes will definitely put it there. Thank you!
Issue 39841 - android - Nexus 7 4.2 Auto Brightness fluctuates. Have to disable to get unit bright enough without constantly changing in the same environment lighting. Worked correctly in 4.1 - Android - An Open Handset Alliance Project - Google Proj
Issue 39841 - android - Nexus 7 4.2 Auto Brightness fluctuates. Have to disable to get unit bright enough without constantly changing in the same environment lighting. Worked correctly in 4.1 - Android - An Open Handset Alliance Project - Google Proj