Longtime pebble user here. The main things are the always-on ePaper display, long battery life (they claim this new gen's battery will last a month!), and the hackability. I personally love the user interface and charming animations!
Many years ago, before Final Cut Pro x my cousin asked me to help inject some video from tapes and keep the time code. In Final Cut Pro. I couldn’t figure it out.
So in desperation I read the manual. It was seriously well written and I understood the program, what needed to be done and how to do it.