I'm ordering my nexus 4 at the beginning of next month. I've always had issues with OEM skins, and I didn't even know it! I Kept wondering why every android phone was a little different even on the same version. Then I learned about skins and vanilla android, bought a nexus 7, and I tell you I am never buying a non nexus device again.
But i gotta say, while I am a tiny bit worried about the glass back and plan to be even more careful than I already am with my phones, I am a little puzzled by the amount of dread concerning it. People talk like it's as fragile as an egg shell, one tiny bump and it's shattered. But I'm thinking, all phones are already completely covered with glass on one side, the screen. This does raise the likelihood of getting broken glass a little IF you drop it on a hard surface... Whereas usually if you manage to drop it STRAIGHT flat on its back, from not too too high, you MIGHT be OK, now you could still be in danger. But I fail to see how most little bumps on a corner, fumbles onto a carpet etc. that don't harm the half already covered in glass would be any more harmful to the back.
Maybe it's just me but, short of an all aluminum body like the new ONE, I'd take glass over plastic any day. I figure if my screen is safe from the every day little fumbles my phone might go through, the back probably will be too. And if I drop it from a few feet or more, straight onto concrete, unless I'm terribly lucky I'm going to have broken glass either way. I saw a video from one of the pocket now guys who dropped his naked N4 and broke the glass, but it was the screen... The back was perfectly fine. I'm not too worried about it. I'll take precaution, but I'm not going to be paranoid about it.