Software upgrades are supposed to improve the performance of a device but I have had a slightly different experience after upgrading the Google Nexus 7 to Android 4.2.1.
Another new problem with my Nexus is the flickering screen. The device screen would intermittently fluctuate between being bright and dim and this happens more in a dimly-lit environment.
I wasn’t too sure if is was due to faulty hardware - this Nexus device is about 5 months old now - or a software issue but the flicker was especially noticeable on white backgrounds - like when viewing web pages inside the Chrome browser.
It turns out flickering is a known issue in Nexus devices and users have mostly reported it after upgrading to Android 4.2. For some Nexus owners, the flicker is more noticeable when the Wi-Fi signal is weak.
Fortunately, the fix is easy. Go to your Android Settings -> Display -> Brightness and turn off the option that says Automatic Brightness. I have moved the brightness slider level to around 40% and the flickering issue hasn’t surfaced since then.
Maybe the issue is due to the ambient light sensor on the Nexus device. If this fix doesn’t work for your device, the other suggestion includes turning off Wi-Fi power management. This is available under your Settings -> Wi-Fi -> Advanced -> Wi-Fi optimization.
You may not get the most optimal battery life on your Nexus but at least these suggestion may fix a more annoying problem.