This iPhone UI proposal is well thought out but it’s fundamentally too complex for most user needs. I found the extra bottom row of apps especially unnecessary; I’d bet if you were to look at user stats users rarely invoke the double tap app switcher for apps older than the four previously used.
However, major props for Verge forum user brentcas identifying two major problems with iOS 5. First, turning on and off WiFi, Bluetooth and brightness requires way too many taps in Settings given how in demand they are. In addition Spotlight searching should be more accessible; as users add more apps, sometimes an open ended simple keyboard search is ideal to cut through the complexity. I hope both issues are addressed in iOS 6.