There's a fair bit of 'easy' customisability in a Pebble.
And the battery life of 'aroundabouta week' is great compared to the 'charge overnight' crowd. I like to have a watch on at night, and I can silence my phone and have calls vibrate the pebble to wake me up if needed, but I sleep pretty lightly.
Notifications are good (with an add-on app), Phone control is easy (with an add-on app), there's a bunch of little apps for just about anything. Download the Pebble app for your phone (no need to get the hardware to install the app) and have a poke about in the app store section to see what's about.
There are programs that allow you to make your own faces with a builder app on your phone. You can get apps for it that can pull any JSON data you want from a server, and the actual dev environment used to make 'real' apps isn't too bad to work with.
And the original plastic pebble is pretty cheap and waterproof to 5 atm. (um, swimming and showering and stuff), so I rarely take it off.