Thsi is why I didn't get the Plus and got Apple Care+
Aside from the fact that it was just too big to handle comfortably, the Plus struck me as a damaged phone waiting to happen, because I just didn't see it being durable enough for how I carry and use my phone. I'm hard on my phones, but with a decent case and screen protector, my previous iPhones all were in mint condition when I sold them.
I'm not as sure about the 6 (let alone the 6 Plus). Common sense tells you that the bigger size creates more leverage/stress on the phone when carried in a pocket, and it will interesting to see whether casemakers come up with highly rigid cases to counter this. Because of the curved glass, it's virtually impossible to protect the edges of the front glass unless you have a case that does that. The rigid film screen protectors won't extend that far. The other thing I've noticed is that casemakers will have to incorporate deeper lips into their designs, because the Spigen case I got barely protects the screen because the lip doesn't take into account additional height of the curved screen.
The larger screen is great, and now I wouldn't go back to the 4" iPhones, but my impression is that this is a more delicate device and has to be treated as such. Which is really unfortunate.
Personally, damn that weight and thinness, I'd rather have had Apple make the aluminum case thicker and deeper (more sturdy) so it could have put a bigger battery into this phone!