As someone who is tasked with supporting hundreds of iThings, among other duties, I can say that Apple devices, including their batteries, are pretty tired and worn out after about a year and half of use in an enterprise environment. Oh, except for the somewhat fragile screens, they are built pretty well, but I have a drawer full of iPhone 4s and now some 5c devices that have crummy battery life and that exhibit erratic behavior like random reboots, lockups, unresponsive screens, poor radio reception, etc.
To be fair, when we had Blackberry devices, we had a drawer full of those too, though at least you could easily change the batteries and backup/restoration of data was not an exercise in frustration (well, not as much anyway) like it is with iTunes. With BB you could at least selectively backup and restore, not the "all or nothing if it feels like working" that you get with iTunes.
I'm sure if we had Samsung or other Android devices company-wide, we'd have a bin full of problem children too: Enterprise devices see hard use and are not treated as gently as consumer devices.
The iPhone 6 looks a bit fragile to me. The myth that Apple builds better quality hardware than others is only true when compared to the cheapest offerings from other companies.