Mine, 32GB + mobile data directly from Google Play USA, is so far in good conditions. Sometimes I feel a little squeaking, but not in the left upper corner, where it occurs when there is a screen lift. And I think it's the SIM-Slot that causes that, and either ways it sounds more like it's the back cover and not anything else, which would worry me.
Had a couple decent falls, but no screen cracks yet. Not using a screen protector yet, and I haven't seen a scratch so far.
Received mine (32 GB, WiFi) in November as a birthday gift...purchased from Sam's Club (who knew????). First one did not load 4.2 update...the little android guy was dead on the screen all three times the update tried to install. Called Google customer service and they were very helpful as they tried to troubleshoot whether it was a Google issue or just a bad unit. We returned it for another unit...no problem. Second one has worked perfectly. Love it.
I decided to tell my saga on a public site. I ordered the Nexus 7 in mid-December as a Christmas gift to my children. Opened on Christmas and plugged it in and it never fully charged. I called on 12/26. I was told to do a few things and try plugging in. I did that and nothing. I called to return. I was told a new device would take a week. I sent the original device back on 1/3. A week after they said I would have I called and was told it would take at least two more weeks. I knew that the original device was scheduled to be delivered back to Google that day. I asked for a refund. I was told it would take a few days to process. I called back and was told two weeks. I called after two weeks. Two weeks of business days only. Called on Business Day 15. They would have an answer 48 hours later. I asked if that was business days and was told I would have an answer by Saturday night. I sent an email on Sunday and again today. Still no refund. The response tonight was bull. I guess Google should stick to search engines.
Got one about a month ago. It creaked on one corner for the first week, but for whatever reason stopped after that. It has crashed occasionally, but I assume that has to do with the OS rather than the hardware.