Those new Nexus 7's sure are nice. Unfortunately, a number of those shiny new tablets have a manufacturing issue that makes the screen uneven with the bezel. Google's solution is to have you send it back in, but why waste your time considering the problem can be fixed by simply adjusting a single screw.
All you need to perform the adjustment is a guitar pick or coin, and a very small Phillips screwdriver. Also note, opening up your tablet will most likely void your warranty, so consider that before proceeding, though no one has reported seeing any warranty seals.
Use the plastic pick to pry the back of the case off. Start at the top and move down the sides.
Find the screws holding the bezel in place. One of them will be loose, but tighten all of them just to be sure.
Then simply snap the back cover back into place and you're done!
Now that you've fixed that uneven screen issue, you can move on to bigger and badder things with your Nexus 7 tablet, like rooting it.