I was listening to a podcast that was recorded later the day of the announcement, and they were ordering and getting them shipped for next week. So, I guess a month's worth of production or so is sold already.
It's a LOT more rugged than it looks. I'm not easy on them either. I did manage to mess up the screen on my first one (series 3) very shortly after I got it in 2017, but I was wearing it while working on my tractor and kinda dropped a mower deck on it. Got it replaced under AppleCare for another Series 3, and bought a Series 5 a year ago. I haven't ordered a 6 yet, but I probably will before too long. It'll be really nice to have that oximeter.