Besides being a bit bulky, the doorbells (I have the Doorbell Pro) have plastic or rubber button that does not hold up very well. The doorbell is not used very often, however it rips and cracks due to the heat and germophobic people using keys or other objects to push the button. I have not seen the actual button in the spare parts section and these doorbells are very expensive.
I would like to see a capacitive touch doorbell to iliminate the used of temperature sensitive or moving parts. A doorbell like this might even make the doorbell look smooth.