I been pleased with most functionality so far, but I'm coming from a Pebble and an iPhone. I've used the watch as a phone 20 or so times, all with the other person saying the call is crystal clear. OK Google stinks! No real functionality there. I've tried a number of times with "OK Google... call Tom", etc. No luck. It only looks up cards on the internet for "Toms". I can "OKG" "start Agenda" and see my full calendar on the watch or "start phone" only to navigate by finger to a contact to call. After navigating by finger to the messages app and picking a contact on the watch, I can send a message by speaking the text, etc. I'm using IFTTT to add some alert functionality to it and am happy with those.
Weirdest part is I have paired it to my iPhone via bluetooth multiple times with no issue, but I still have no way on the watch to navigate to Wi-Fi settings or Bluetooth! Those icons just don't exist on my watch! So I have not paired it to my home network or a headset... as far a as I know, I can't!
Because of I thought this was due to the iPhone, I was just minutes away from switching my iPhone to a Galaxy 6 at the ATT store the DAY it was cancelled. They were already resetting the store (as they do every Thurs) and all of the reps there said nothing about my watch, even after asking me about how it was working.