If you've ever done an ESD test, you will know that buttons, LEDs and dispays can all be a route in for an ESD strike. I would therefore look at including transient suppressors on all IO lines, whether buffered or not. As for the actual buffer, I'm not in favour. The micro IO pins are often as tough as a buffer IO pin, and the extra circuitry just makes the product less reliable. I assume that you are not planning to make the buffer replaceable (i.e. it acts like a fuse, and gets replaced if it fails).