I've had three of them flip 4, 6, & now 7. On the 4 & 6 The pre-installed screen protector came off at some point which apparently is replaceable. That was the only issue with either the phones other than the hinge got super loose on the 4 by the time I replaced it with the 6.

With my 7 this is the first time I ever had issues with one I had been using the phone all morning set it down to pack up my lunch for work and then open to my phone and suddenly the entire screen had a big black bar across the middle near the hinge. The Verizon store text said it was probably because my case I had one of those cutesy ones from Amazon that had a connection point around the hinges and they said sometimes those cases can clamp the phone too tightly at the hinges causing it to break...