After a month with a Sony Smartwatch 3
... it came "free" with a phone upgrade, not something I bought separately. So after a month, my impressions.
First, the good bits: It's quite a nice watch, certainly more stylish than the 15€ Decathlon digital thingy I usually wear. It doesn't look too cheap, and it's comfortable. As an IT worker it's got a certain geeky charm. It needs charging every 3 days or so, which isn't too onerous. (It's also worth pointing out that discovering the charge is running low isn't anything like as irritating as discovering your phone is about to die). It's waterproof. The vibrate notifications are quite handy if, like me, you prefer not to irritate your coworkers with endless beeping whatsapp notifications - it's always 100% something's happened, which isn't always the case with a phone set to vibrate and sitting in a pocket or bag. It makes a reasonable remote for your (phone) music player.
The not-sure bits. It's got a GPS and you can use it for navigation. Obviously not much use when you're driving, but could be good when walking. I haven't tried it, though. Not sure about battery life with the GPS activated, either.
The bad bits. Except they aren't really bad, more just a reflection of the pointlessness and limitations of the watch. Reading messages is a trip down memory lane: it's just like trying to read stuff on a Nokia candybar phone. It has a certain nostalgic charm, but it's still crap. You can apparently talk to your watch and get it to do things, but you look like a twat. You can open apps on your phone from your watch - but why would you when you still have to use the phone to actually do anything with the app? 3 day battery life is OK for a smartwatch, pretty crap for any other of watch. The UI is confusing, sometimes you swipe down, sometimes you tap it, sometimes swipe to the side.
TL;DR: it's quite nice, but ultimately pointless. It was free, so I use it. I wouldn't spend 200€ on one, though.