"for all its improvements, it's a big step back ergonomically"
The funny thing about handheld devices is that we each have different hands. Double-fisting both of my iPhones right now, the 4 feels a lot better in my hand. If you have bigger hands with me this probably isn't true for you, though.
I was reading this thread on my 4, and when I read your comment I looked to see how I was grasping the device: in landscape mode, pinched between my thumb (below) and middle finger (above). I was scrolling with the index finger on the same hand. The old design was poor for a 1-hand, 2-finger grip like that. I wouldn't want to go back.
The funny thing about handheld devices is that we each have different hands. Double-fisting both of my iPhones right now, the 4 feels a lot better in my hand. If you have bigger hands with me this probably isn't true for you, though.