I have average, or maybe slightly larger hands than average. I have had the S3 and Gnex, and they are both easily navigated with one hand. It takes minimal effort and .2 seconds to adjust your phone in your hand(using only that same hand) to pull down the notification center at the top of the screen. I mean how lazy are people?
All this two handed talk to use a 4.7" is a joke, i tons and tons of girls at work using the S3 all the time, none of them are bitching about the size.
I will say though ALL of these issues for the people that do have issues could easily be resolved if they JUST PUT THE DAMN CONTROLS AT THE BOTTOM OF THE SCREEN INSTEAD. Its a simple fix...
Put the notification at the bottom, swipe up to get it, put all menu buttons, or any buttons at the bottom..easy again. There would be ZERO reasons to reach to the top of the screen then, unless you want to click a link or something maybe, but then all you gotta do anyway is scroll down a little to avoid that...who knows though, that may be to much work for some people