This is why I think the single "home button" interface was one of the most brilliant UI innovations ever (no, I'm not joking) and Apple was insane to abandon it. Hit home (maybe twice, if you weren't on the very first screen of apps) and you're back to somewhere you know. Hit it too many times, nothing bad happens. And it's a physical (or, convincingly physical-imitating) button! It never moves around, it's always in the same place and you can feel it! It's one of the most comfortable, reassuring, and for normal users practically useful UI elements ever created. Even if you hold the button down and get in a "weird" mode (app moving and deleting mode) the way out is to... press the button once. It always works.

No other buttons (visible on the face, anyway) to confuse it for. It's right in comfortable reach of the thumb. "Which button do I push again? Oh right, there's only one."

(I also think going to "swipe up to unlock" instead of the brilliant slider they had before was a big mistake, as far as reducing the level of comfort for the median user)