There is a good reason that some new cars are coming out with push-button starters.
Some makers, including Mercedes, Cadillac, and I believe Dodge with the '03 Viper (not sure on that tho), are coming out with totally passive security/starter systems. You still have a key fob - like any normal alarm/starter/remote entry - but the fob transmits a signal automatically. When you walk up to your car, you leave the key and fob in your pocket. The doors unlock themselves when you get close. And the fob allows pushbutton starting of the car - no pressing a button to unlock the doors, and no turning of the key to start the car.
How nice, walk up to your car, open the door, get in, put your foot on the brake, push a button, and go. No fumbling with keys for anything.
Other than these systems, push-button starters are all for "looks".