My wife has a Prius with keyless entry/start. The keyfob hides a physical key that you can use to unlock the door and you can insert the keyfob into a socket in the dash if you need to (if the battery dies). Works great. Plus the batteries in the keyfob are readily available and easy to change.
I love being able to unlock the doors and start the car without needing to get the keys out. Makes it that much harder to lock my keys in the car.