As part of my recent purchase of a Samsung Galaxy S8 I got a Samsung Gear S3 - Frontier smartwatch as well. It is my third smartwatch, but the first operating Tizen. The previous two, a Sony Smartwatch 3 and an LG G Watch R, both run Android Wear, the latter AW2.0 but the former left languishing on AW1.5.
I recognise there is a thread addressing charging problems on an S3 but this is more about the watch generally.

I have had the watch for about ten days now so here are some of my impressions of it and comparisons to my other watches.

Hardware

Better battery life than the GWR. I can generally get two days in normal use (WiFi is turned off on both). Not quite as good as the SW3 which could be stretched into a third day due to it's transreflective display.

Charging via the proprietary wireless stand means having to take a specific device on the road with you to recharge. Same as the GWR with a specific mount required. The SW3 is alone in using a micro USB port for charging. It has a rubber cover for waterproofing, which I have somehow managed to keep intact. The advantage being less cables to take away with you (I am on the road quite a bit with work). I have ordered an additional charger for the S3.

The display on the S3 is great and easily on a par with the GWR, both being AMOLED. The SW3 comes in a distant third in every measure except direct sunlight where its transreflective display makes it readable when the others washout. I have the S3 set to always on, albeit with reduced components on a black background when in dim mode.

The strap on the S3 is a standard 22mm one (same for the GWR) although it does have a proprietary quick release pin mechanism. Standard pins look like they should fit anyway. There are different sized sets of straps supplied with the S3. The larger one was on the watch and is the one I use. It is a large watch on my wrist so it must look absolutely huge if you need to use the smaller strap! In use so far the S3 strap is the least comfortable to wear, the SW3's rubberised gel band being the most comfortable. The downside for the SW3 is it's strap is proprietary and expensive to replace and when Sony did release a 22mm adapter it is both expensive and ugly. I will probably replace the band on my S3 at some stage, although the asthetics of the Frontier S3 mean there are less good looking strap options than the Classic (imo).

The rotating bezel and two buttons are great and allow much better interaction than the singular buttons on my other watches. The bezel particular allows operations while keeping my fingers clear of the screen. I do wish the accelerometer allowed gestures like Wear does though.


Software

The operating system is probably the biggest limitation of the S3, but only if you are the type of person (geek) that wants to be able to do more with it than what comes out of the box. While the Samung App Store has more and more apps each day it reminds me of the early days of the Google Play Store, where apps are often poor ports of apps for other operating systems.
I was expecting extra interoperability between my Gear S3 and my Galaxy S8, but apart from the likes of S Health, it provides no more than my Wear watches do. In that respect I believe Samsung have missed a trick and could do so much more with the symbiosis between two of their premiere devices.
As I mentioned above, the interaction using the bezel and buttons is great, and your can also use swipe gestures on the watch face. One thing I miss from Android Wear though is the ability for one handed gestures. To be able to flick through and dismiss notifications without having to raise your other hand to the watch is a great feature and one I'm hoping may come to the S3 eventually.
Being able to assign functions to the buttons is a good feature, as is being able to put the apps in what ever order your wish in the launcher.

That will do for now, except to say that the S3 is a good device and could be great if it's software can be made to do more. I believe that Samsung could do more with it with respect to the way it works with their flagship phones. Compared to the SW3 that I paid $300 for, and the $120 that I got the GWR for, I think $600 is a little expensive (on a par with Huawei , LG, etc). I don't think I would have bought it without the bundle deal with the S8.