Comment: Re:Goodbye iPhone, Hello Nexus (Score 1) 360
That back button's behaviour has been consistent for me, at least on my Galaxy S.
If you're in an app and press the back button it goes backward in the app. When it reaches the "main" or "home" screen in the app, it closes the program entirely and returns to whatever was open prior to that. This is confirmable for me by going to the task manager (holding the home key and tapping "Task Manager") to see what's currently running.
It's far more consistent than my old iPhone 3G, where there is no back button, and every app had a different idea how the UI should be done and where the buttons should be. Not to mention there was no easy/intuitive way for me to close an app or navigate around options.
The one thing that's consistent on Android is that there's a context menu and a back button, making it easy to navigate around a program.
It has a very consistent behaviour, unlike a lot of apps on the iPhone. I don't think I'll personally ever return to an iPhone. I've gotten so used to having more intuitive navigation controls.