The screen interface is more accessible than the buttons. With buttons I've to feel my way around since there are three on the right side. Also I've to support the watch from the side opposite to the one where the button is being pressed. Also with gloves, jackets etc I've to wiggle my way to be able to press buttons also sensing which button I'm pressing is not easy.
For me, being able to operate the buttons by feel is a key feature, and I find it pretty easy to do on my original Pebble. It's useful for controlling music playback or dismissing alarms without having to look at the watch.
I agree that there are disadvantages too. One of my jackets does make it harder to access all the buttons. And scrolling through a list one item at a time can be more annoying than just swiping and tapping on the item you want.
