I haven't used a Pebble, but I wanted to mention something I have seen praised a lot on HN and elsewhere. Apparently, the Bluetooth stack on a Pebble is absolutely legendary: reliable, dependable, robust, you name it. It still works reliably today seemingly thanks to their very diligent software design.
I hope that element of it will continue to exist as-is on these new ones? I mention this because Bluetooth is still generally speaking very meh.