I really don't give a damn about the phone being fancy or expensive looking but I do care about ergonomics. With these bigger screen sizes they should make the phone better to hold. The iPhone 6S is a bit slippery without a case and the curved edges provide little grip.
Based on my current Z5 Compact which is more angular, the back of a phone should be smoother and curved to be pleasant to hold, fitting better in your palm. There can be more edges on the front. Sure, a curved back won't sit flat on the table but that's not what phones are for. That way they could also add in a bigger battery because having a thinner phone isn't really what anyone needs.
I also hope they get rid of the home button or at least place it somewhere on the side where it's better to reach. I really love how they've done it on the Z5 Compact, the power button and fingerprint reader is in a perfect position when you grab your phone.