There isn't much out there yet in terms of user reviews so I thought I'd give my initial impressions as Ive only had it a couple days.
First, lets talk about the size. Before I bought it, everything I saw on the internet made is look gigantic. Don't get me wrong, its a big watch but not ridiculously so. During the purchase, I was actually relieved that it looks smaller in real life than in pictures. Plus its incredibly comfortable. It's so light, you hardly notice you are wearing. They designed it well.
Secondly, I wanted to talk about usability. Yes, you can make and received calls regardless if you have your phone in the room with you or not. It has its own sim card. A neat feature that you can set your phone to call forward mode once it loses bluetooth connectivity. So you dash into a store and your phone is in the car, calls go through to your watch. This all happens seamlessly. I'm not sure about messages yet, haven't had that happen yet.
They little keyboard for sending messages, I thought would be a nightmare, but samsung pulled it off for the most part. They keyboard has swipe thats pretty dang accurate. With it being so small keyboard, you are going to run into mistakes in your typing but not a lot once you get the hang of it. Between swipe and predictive text, you should be good.
This is my first wearable so I was totally confused on the whole concept at first, but downloaded the app, set it up and started playing with it. A day later, totally get it and how it works. Super easy.
Battery life is hard to comment on as I haven't had it very long. Thats why I only gave it 4 stars. I set a dark background because I read it saves battery on amoled screens. At the end of the first day, I had it on constantly playing with it but it still had about 18% power left. Charged it overnight. Today with moderate use I'm at 63% at 11:30pm.
The screen is amazing, so crisp and clear. Colors look great, you can customize your screen but not as much as I'd like. You can pick a background from your own pictures or ones the watch offers and a set of clock faces. You can get new ones from the samsung store, some of free and some are paid.
I'm happy with my purchase. There are times when I just don't want to take my phone, like clubs. Has all the info I need for durations when my phone stays home. Contacts, calendar events, texting, calls. One note about calls. If you are at a noisy place, expect to go outside to take a call on this watch. The speaker is loud enough but not loud enough for a loud place. Ive asked about how my voice sounds and they couldn't tell a difference between calling from the watch or my phone. Sounded just as good.
Sorry that was long winded, but hope this helps.