I actually picked one up last week since they became available at best buy. I'm loving it, especially with Android. The stock app is nice, but there are a couple third party apps that really open up the functionality of the pebble. Also the integration with runkeeper is just awesome. It holds a charge for about 6 days, even when using runkeeper once every day or two. I'm not sure how the iOS app is, but on Android I have the pebble doing a lot of work. I can read and quick reply to sms and email, and you can even check your twitter/facebook from the watch (not that you'd really need to but it's still neat).
I love being able to see who is calling or texting me with a quick glance. I am often in setting where it is inappropriate to pull your phone out/have the sound on so the Pebble is an easy way for me to determine the urgency of the call.
I am very glad I picked one up. I think it puts the metawatch to shame, I was using one of those for several months and the phone app is so bad on both iOS and Android. Also my metawatch often just freezes with no way to do a reset. So far I have had 0 issues with the pebble. I get my notifications within a second or two after they hit the phone and I've had no connection issues. Loving it! I strongly recommend it for any watch junkie, fitness junkie, or for someone who can't always be staring at their phone and still wants to see who is calling.