My only complaint is they try and be clever and detect when you move your wrist up to look at it, so it auto-shows you notifications. This sucks because it's not totally reliable (so half the time I press the button to bring up notifications and it ends up dismissing them because they are already in view, and other times it triggers due to an incorrect motion). I wish you could turn that off but I haven't found a way yet.
I've had this watch for about 3 months now. The first charge only lasted about 2 weeks but after that I actually got more than 30 days on the 2nd charge and going strong on my 3rd charge now, so the battery life claims definitely are true (though I did uninstall the weather app cause it was useless).
The build quality is good. People say it's a little thick but I guess my arms are big enough that I don't notice. I got the leather band and it's never felt uncomfortable to me.
I would recommend a screen protector (Amazon has some good fitting ones for cheap) but that's probably because it's been a decade since I wore a walk and got a tiny scratch because the first day I wore it I accidentally flailed my arm towards a brick column at work. It scratched the face a tiny bit (not really noticable) but I feel much safer with a screen protector.
Any other specific things you'd like to know I'm happy to answer.