Not every screen needs a back button. You can't hide a hardware back button.
I'm with Apple on this one. The back-arrow button in the toolbar reminds me I'm in a hierarchal app, and the label reminds me what the prior screen was. It's just the opposite for me: every time I use an Android I hunt around the screen for the software back button.
As the hardware buttons are generally lit, you could de-emphasise it by removing the light. I had a Motorola java phone which did just this.
The failure of the Apple hierarchical model is it's app-centric, unlike Android which is activity-centric. In a perfect world we could have software back buttons which worked like Android, but I wouldn't trust developers to implement that consistently.
If there is no place to go back to (i.e., you just opened the app), back takes you to the home screen.
Besides, just as you can't hide a hardware back button, you can't hide the wasted space sitting to the left and right the iPhone's "go home or randomly open Siri" button.
I'm with Apple on this one. The back-arrow button in the toolbar reminds me I'm in a hierarchal app, and the label reminds me what the prior screen was. It's just the opposite for me: every time I use an Android I hunt around the screen for the software back button.