[Samsung Gear S2] Avatiach:
My quick summary after 1.5 days of usage. Bottom line - I wasn't really sure what to expect, but I like it quite a lot and looks like I'll be keeping it around. Here's a quick summary of the points that were important to me, in case folks find it useful:

* Size, looks, comfortableness: I'm probably average size (man) wrists, and it looks quite nice. Not too big, not too heavy, very well built. It's not always super comfortable, but I think part of it is just getting used to having a watch at all after many years of phone-only :)

* Battery life: Very pleasant surprise. I'm writing this at 9:45pm with about 19% of battery left. My day looked like this:

-- Between 8:30am and 8:30pm:

---- Watch was connected to the phone via Bluetooth throughout the day

---- 3G and Location were ON but not sure if the watch used them since it was connected to the phone as mentioned.

---- Wifi and NFC turned OFF

---- Brightness level at 2 (wasn't much outside, 2 was more than enough inside)

---- By 8:30pm (12h), the watch was at about 52% battery

-- 8:30pm to 9pm

---- Went on a short run without the phone, watch was connected to phone via the mobile network

---- Played music from the watch via a Bluetooth headset

---- Used the Nike+ app to track the run with Heart Rate Monitor turned to constantly on

---- Brightness level set to 2

---- By 9pm the watch was at about 23% battery.

And now at 19% as mentioned, 9:45pm. I actually didn't expect it to hold on so nicely.

* Apps: Clearly the big issue with this watch. There are very, very few apps. I do have to say that it's hard to tell on what I'm missing, since I never used an Android wear phone, so I can't really know what value I can get from apps on a watch like this. For now, I don't feel like I'm missing anything major (except for running, more on that shortly). It definitely solve my biggest need - use the phone less next to my 18-month-old son :)

* Running without a phone: Not much of a runner, but this one was quite important to me. The bottom line is that it works - I used the Nike+ app, it tracked the run, I could listen to music via the headset and notifications from all my apps arrived directly to the watch as it was using the cellular network. So I'm fairly happy! However, I would rather use other apps for running, and I couldn't find yet a way to select a specific workout and be guided by it - I could only start a generic run. Also, while it recorded all the run details, it didn't record the course itself, only the distance. That said, I didn't yet read any of the documentation, so I might be missing something. I can't speak to the accuracy of the steps/heart rate monitor - in terms of distance, the watch logged a slightly shorter distance that what my phone used to log on a similar run - not sure which of the devices is the more accurate one.

* Other stuff:

-- I read complaints about vibration being too weak - I didn't notice this. Using the "strong" setting I could definitely feel it. It's not super strong, just a gentle nudge, but that's the strength I would probably have chosen even if there was a stronger one.

-- Music - I could control any player on the phone, not just Samsung's. Wasn't sure about that one and was happy to confirm that's indeed the case

-- I could get notifications from any app, and could respond to messages directly from the watch even on apps that don't have an S2-specific version (such as Whatsapp - not sure if this will be the case for all apps, just my experience). However, for such apps you can't initiate a message, only respond to ones you get first. I was also forced to move to Samsung's messaging app (from Textra), which was a small annoyance, but nothing major as I'm not a heavy SMS user.

-- Voice - Can't speak much about it since I'm not much of a voice user. Didn't try it, but I definitely like having the keyboard option (which I understand isn't there on all watches). The keyboard does support the same full language array as Samsung's keyboard on the phone, which is great for multi-lingual folks.

* Negatives:

-- On the first day I played around with various ways to connect the phone and watch (phone on wi-fi, watch on cell, then the opposite, with/without BT etc). At some point, notifications stopped arriving to the watch. After restarting my phone, they came back. This can be caused my many reasons (phone ROM, my wi-fi etc) and I didn't encounter it since that one time last night.

-- When connected via Bluetooth to the phone, it seems like the Phone battery drains a little faster. It's a little hard to tell on these things, but that was my feeling. Didn't test yet what happens when they're connected over the cell network

-- Apps - As mentioned, not 100% sure how critical it is, since I haven't seen what apps can do on a watch, but would be nice to see more of those available, especially on the running front. If I'm Samsung, I'm totally forming a small team of developers and turning them into an outsource shop for major apps, developing S2 versions of such apps with approval/review of their originating companies, rather than waiting/hoping they'll build it themselves.

A lot of this is personal preference, of course. My experience has been pleasantly positive so far and if things continue like that looks like it's a keeper for me. Happy to try and answer any specific questions if I can (not much free time these days, but will do my best :) ).

Edit: Forgot to mention that my phone is a Samsung note 4, running a modded version of a stock TouchWiz 5.1.1 Rom.