Shattered screen. And a weak battery that I bought a replacement for at an iPhone repair store.
First of all be aware that the Display Panel Assembly is not the same thing as the Front Panel Assembly. You save money doing the Display panel assembly kit but it's a bit more treacherous. Otherwise, besides for a few 15min sessions trying to get a single screw in place, the %#*@ thing works! Can't believe it. Snapping the front panel down was one of the more exhilarating feelings I've had! (I know this doesn't make me look very worldly).
During Home Button Assembly, when you're putting the phone together, don't worry that the Home Button doesn't "pop" like a regular iPhone button. It will get that "pop," assuming it's placed right, once you re-connect the front panel. Spent a few hours agonizing over whether I should dig the membrane further down until I felt a pop with the home button or proceed with the possibility that I would have to go back and redo the Home Button Assembly. Fortunately, the instructions were simple and correct - don't second guess yourself too much!! (easier said than done). Also if you're doing a screen repair, might as well do a battery replacement as well. It's not much harder and you're already in there.