Maybe functionality is in the eyes of the beholder... but Pebble can most definitely do all of those things with the proper app: view calendars/agendas, send canned SMS responses, and view upcoming weather. You don't have to "ask" your device to do it, just press the right buttons. Despite the "coolness" factor, I find it preferable and more discreet to press buttons, rather than using a microphone or swiping a touchscreen. Depending on the app, you can literally cycle through the three things you've mentioned in three button clicks. [1] Also, if Pebble has a killer feature, it's that its battery life crushes anything else I've seen thus far, regularly lasting through 5 to 7 days of 24/7 wear and bluetooth connectivity...I don't think any Android Wear device can do that yet, but I would be really interested in looking at them if they could.
EDIT: FWIW, I don't use Google Now on my phone itself, so I admit that some of the novelty or utility of what it can do from your Android Wear device might be lost on me.
I have a Pebble Smartwatch and it definitely does not have 5-7 days of battery life. More like 1.5 days (2 if your lucky). Also, I do think the fact that Android wear makes so much functionality so easily accessible is a huge deal for smartwatches. You just say "Ok Google". The whole point of a smartwatch is to seamlessly integrate technology in your life. That means our interactions on them need to be quick. You can't get that if you have to poke around the Pebble watch UI for 15 seconds before getting to your app and THEN sending out the text, or checking your calendar etc.
Unlike the sibling posts, I have automatic backlight turned off and it regularly lasts a minimum of 5 days. On the fifth or sixth night, I charge it over night and I'm back at it.
With respect to "OK Google," more often than not, I find myself in places where talking to my watch would strike me as obnoxious: the office, outdoors, the subway, an elevator. Sure it's quick, but again, a button press or two strikes me as being more effective in those situations. I really would only think of using voice commands in my own home, or in the car. I guess it's all a matter of personal preference... I know exactly how the UI of the Pebble app works, and exactly what it's going to do in a certain amount of time when I press a particular button, which feels pretty seamless to me.
Lest I only say good things about Pebble, I have to mention that in a little over a year of ownership I'm on my 4th one: 3 RMAs due to persistent screen defects. This 4th one should be sent back, too, but I've yet to get around to the RMA process again. Two of the RMAs were within 1 year of purchase, and one was beyond, so my credit goes to their customer service.
You must be doing some very intensive things with your Pebble. I have the automatic backlight turned on (turn on when I shake it), and mine regularly lasts 3-5 days, even when I go running regularly, which happens to trip the automatic backlight for most of the run.
I also use it to track yards I go swimming, Runkeeper for tracking my runs, and miscellaneous things like the music app and the Swarm app.
I definitely get many days out of my Pebble (I don't bring the charger on weekend trips, etc).
I completely agree though that the Pebble is best as read-only and notify device. Interacting with it, even to change apps, is a chore. But I don't really see the point of putting a lot of interaction on a watch when, at some point, it's easier to just pull out my phone.
I have Misfit installed on my Pebble which monitors my every step during day + sleeping cycles during night, so basically using accelerometer 24/7 and I'm getting around 3-4 days of battery with that usage.
Also I'm getting notifications every few minutes (email, facebook, skype) + vibration is on.
I have a pebble as well and ditched it. You can do exactly the same thing on android wear as pebble. There is a launcher to run apps. Touch screen instead of buttons. Full color instead of monochrome. Battery life is about 2 days for me which is more than enough.
The pebble has waterproof, and longer battery life. But I'll trade that for android wear.
[1] http://www.finebyte.co.uk/?page_id=9
EDIT: FWIW, I don't use Google Now on my phone itself, so I admit that some of the novelty or utility of what it can do from your Android Wear device might be lost on me.