Unnecessary design
I've had an iPhone for years now and i like them, but I cannot fathom why Apple makes the damned things out of glass! I mean - why? The first thing anyone does with a new phone is to stick it in a case so that it doesn't get so easily broken - ironically, even more important when the thing is made from glass! So nobody is going to see the nice swish glass body anyway.
Similarly, I cannot fathom Apple's insistence on making everything so bloody thin. Again - it gets shoved into a (often bulky) case anyway, so adding a few mm to it would allow for a battery that was twice as big, and it would STILL be relatively thin. I think most people would prefer the better battery capacity over something so thin that it's actually difficult to hold (another reason for sticking it in a case).