In the early eighties, there was a lot of controversy about how many buttons a mouse should have. Unix computers often used three button mice. The Xerox PARC computers, which most consider to be the ur-GUI for both Microsoft and Apple, used three button mice. The first version of Microsoft Word shipped in 1983 with a two button mouse. Apple took a different course: first the Lisa and then the Macintosh, shipped with a single button mouse. When asked why, the Apple folks responded that their research indicated that having more than one button confused the users.
This philosophy continues to this day, and as represented in the iPhone, iPad, and iPod Touch by the single button at the bottom of the screen. The Droid X has four buttons. On the Droid X, there is a dedicated menu button. On the iPhone, if you want a menu, you usually tap the screen. On the Droid X, there is a dedicated button to take you back to the previous screen. On the iPhone, you can sometimes get back to the previous screen through a menu, and sometimes you need to press the single button and navigate back to the screen you are trying to get to. And, it being a Google OS, there’s a dedicated search button. I can see the utility of all but the last one, but then, maybe I haven’t internalized the Google mystique.
There’s a clear choice here: speed and directness versus simplicity, power versus ease of leaning.