Of course, the makers of the watch would be mad at this description: it can do more than that! There's a whole app store! It can control music! There's an accelerometer! It can... well, I dunno. The physical interface is a bit limited. I'm sure there's a bunch of stuff it could do, but it raises the question: why?
But I find the notifications feature worth the price of admission. It's great not to have to dig out my phone to see if a message is important, and the watch's vibration on my wrist is much easier to notice than one from an iPhone that's jammed in a pocket. It's also reduced the amount of "phantom vibrations" and I check my pocket for imagined alerts less often.
This is in contrast to what the Galaxy Gear offers in this creepy, creepy ad:
That's a lot of features! But the ad has to bundle up its people in ski gear or load them down with wine glasses to make their point... otherwise all of those functions are going to be easier to do on the companion phone itself, with its fullsize screen. (One exception might be the camera... but then that gets into the whole realm of surreptitious photography aka creepshots.)
I was trying to quantify the boundary of "useful" to "just nice to have, maybe" and realize the Pebble's sweetspot maps 1:1 with the information on my phone's lockscreen: the time, and notifications that may have occurred. Everything else I'd have to swipe to get to anyway. The watch saves me from having to dig out the phone, and makes glancing at at least the sender if not the subject or some of the content of a message very discrete.
(So, reviews of the Galaxy tend to be pretty mixed: the camera feature is solid, and the "talk like Dick Tracy" seems kind of fun. There are still some fundamental issues, mostly concerning battery life.)
It's an exciting space. The Pebble is meeting my needs well right now, though I might jump on the bandwagon once Apple gets its act together. I think the Gear might be a little underrated, but who knows.
For at least the medium term if not longer, I think connected watches will be much more useful and fun than, say, Google Glass. I got to play with one during the holidays, and man, it was so not ready for prime time... an ugly little screen floating in my vision, looking like an Atari 2600 screenshot from ten feet away, having to reach up and stroke the side of the ugly frames, feeling like I was looking like a freak to people who didn't know what I had on, and a potential creepshot taking perv to those who do... decades from now, it might be useful to have information bounced off some lenses, but right now I'm pretty skeptical about this flavor of ubiquitous computing. (Or maybe I'm just turning into an old codger.)