But! The thumb thing is one of a few things that they are justly considering in design process. It's not like I don't like big screens, but there is no one-size-fits-all, sorry. If I want to read book or comics, check some article on the net without powering on my desktop computer, etc. I can use my GoTab ION 7" tablet (I've chosen it over 10", because 10" are too big, 7" really looks like optimal size for book reading and such purposes). But my cell, i.e. mobile phone, is, as the name implies, meant to be phone mostly, thus I want it to be mobile. As a mobile thing I want to be able to operate it one-handedly, because it's damn easier and more convenient if I can pull it off from the packet, do comfortably a few taps to check this or that or make a call and put it back in the pocket. Am I a cripple? No, but my second hand is often bothered, e.g. keeping to some grip in the bus or tram. That's why I have Galaxy Ace 2, which is considered small nowadays (compared to oversized phones), having "only" 3.8" screen with quite good density (480x800 gives ~246 ppi). I sometimes do read stuff on the net using phone, but it's not its main purpose, so I wouldn't change my phone for something bigger than 4". Actually I really don't understand this trend of making ~5" and bigger phones. Yet people buy them...
So once in a while Apple do things right and limiting the phone size is definitely a good example.