I've switched back and forth between iOS and Android a couple of time.
I've currently got a Samsung S9, and had it bundled with a Gear S3 smartwatch too.
The S3 watch is kinda neat and I like some of the things it can do but I still can't shake the feeling that it's a bit of a pointless frippery overall.
It's a really nice screen and changing watch faces is easy. The kids love that I can have pictures of them on it.
Tracks steps, distance travelled, some other workout stuff, sleep, can use it to log water/food/caffeine intake (the calorie count and the BPM are possibly a touch unreliable though, and after a day or two of novelty I don't bother with drink counting).
Pairs with the phone super easy.
Controlling the music player without getting my phone out of my pocket is cool, and useful.
It works OK as a 'hands free' device while driving.
Reminders and alerts are useful for meetings & schedules. It's not perceived as being quite as 'rude' to check a watch as it is a phone (it's easier to surreptitiously glance at my wrist).
The hourly 'inactive - get moving' reminder is quite good as I do sit at a desk most of the working day.
The rotary bezel is a really swish interface mechanism.
There's a watch face that looks like the one from Goldeneye on the N64
It's water resistant (but not waterproof)
There's an app that makes the screen go bright white, like a little torch, that has been useful a couple of times.
It's another battery to have to keep on top of (the battery life is pretty good, it can easily go two full days without being 'managed' but at can't really go to three.
There aren't many apps available (although, how many more do we really need
It's quite big (but not as bad as i though).
The included strap is not very nice (easy to change, and does come with a smaller strap too for the more dainty wristed. Same construction though).
I feel like a bit of a twat sometimes using it in public.
When it goes to sleep, it doesn't open on the app I was previously using (eg reminders for a shopping list).
Notification overload, mainly because I haven't set it all up yet, but I get 8 weather updates or so a day from a couple of different apps (phone apps, watch app, google). Similarly, there can be a cacophony of alerts (computer, phone, watch) if I get a few messages in quick succession, again though, I could fiddle with settings to change this.
Do I like it? Yes. Would I recommend it? Um, maybe