Many owners are complaining that their tablets' displays have begun to come apart from the bezel -- the adhesive seemingly isn't working correctly. Affected users are thus complaining to Google but are having difficulties getting anything resolved.
The second issue with the Nexus 7 is dead pixels. Owners are reporting that these black spots appeared after first boot, or shortly thereafter. Obviously there's no real fix for that, so customers who purchased the tablet directly from Google will find info on returns and exchanges here. The company will ask affected users to contact device support here.
I was planning on ordering one this weekend but think I will wait until they can resolve some issues.
Some Nexus 7 Already Plagued With Hardware Problems