Don't recall if u was on that thread, but I did upgrade from a U1 and it was worth it for me.I also have had the U2 since launch (don't I remember you being on the release day thread?), and absolutely love it. I wear it 23/7.
I have some small scratches on the titanium bezel, hard to see except in bright sunlight.
Sapphire crystal is still perfect. And I'm a klutz, constantly smacking into things. My Series 6 with ion-X glass had scratches almost immediately, ultimately resulting in a crack that got it replaced by AppleCare+.
I have my U2 set to charge to 100%, but usually pull it off the charger somewhere in the 90s. Current battery health is 94% after almost 23 months.
Since I need the Sp02 function, I don't see myself upgrading anytime soon. But I doubt the U3 will be a temptation anyhow, considering how well my U2 is doing.
Battery health is now at 97%, I use the U2 for like 38hrs straight (from like 6am day one to like 8pm day two) then put my S7 on for sleep tracking while U2 goes on charger (s0 puck, so slow) til 6am and so on...
I have optimized charging in but charge to 100%, I tried the 80% charge limit but with my usage it dropped to like mid 10% and in my mind being so low is worse than charging to 100%...
So mine is good for another few years, but, if SpO2 comes back AND there is a new health sensor (eg blood pressure) I might get the U3 in black, maybe, gonna wait for the actual announcement.
And I do have AC+.