Upgrading to G3 - worth?

There's no doubt that this phone is much better than my HTC ONE M7, in every way possible. There are a couple of other concerns I have despite the fact that it is dirt cheap at the moment. I can literally buy 2 G3 for the same price as galaxy s6.

Hardware buttons at the back - annoying? steep learning curve?

Battery life due to 2k HD resolution?

Other general comments?