The clickwheel and the digital compass are PDA features that make the biggest difference to me. The Blackberry's clickwheel interface means that you can operate all of it's functions using just one hand and most of them using only your thumb. As a platform for the clearly defined productivity applications that make up the core of their value proposition to business users, this simple and elegant design decision makes the Blackberry a standout. The one handed interface has the added benefit that you drop the device a lot less often because you have a another hand free to deal with all the other other exigencies that crop up when you are mobile. Apparently the RIM engineers also spent a lot of time making the Blackberry rugged, because I have dropped mine over twenty times and it has not only never broken, but hasn't even rebooted in response to the trauma. Your mileage may vary, but one drop meant sudden death for the iPhone. Read more