"Push is everything, and push changes everything," Yach says.

Push means that BlackBerry users never have to go looking for new information; it comes to them, he says. Such functionality completely changes the way users interact with their mobile devices by reducing the frequently with which they need to physically seek out new information.

A quality push application also uses the wireless network judiciously, only delivering information when necessary or when users call for it, he says.

5) Preserves Battery Life: Great BlackBerry applications don't degrade the overall performance of the device, and that calls for effective use of the battery, according to Yach. No matter how valuable an application may be, if it reduces BlackBerry battery life to only a couple of hours, it'll probably hurt users more in the long run that it will help them.

"The best wireless apps use wireless the least," Yach says.