I purchased the series 6, my first iwatch, (actually, my wife did for my birthday) less than a month ago. I've been careful while wearing the watch, but noticed a series of scratches that developed on the screen seemly overnight - the watch looked great then it didn't. (I wish I knew how or when, but there wasn't a big accident that I am aware of.) I wear nice watches regularly and haven't had a similar issue.
Luckily I purchased AppleCare, and they are doing an express replacement. I researched the apple forum boards before making the purchase, and they didn't recommend purchasing a third party screen protector and noted apple didn't sell one, implying it wasn't needed. That seems like poor advice now.
I was prepared for some scratches over time on the aluminum case (I opted for the cellular model) based on what I read, but didn't expect them on the watch face. (It makes the watch look terrible.)
When I get the replacement I plan to use a third party watch face protector. Possibly a coating at Verizon. Any suggestion?
I like many / most features of the watch - the technology is great - and have been wearing it daily for activity tracking. However, if the face remains scratched up I won't wear it long and will likely return to a Garmin model especially for athletics and tracking. (I haven't done what I'd consider a workout in the watch yet as I haven't wanted to scratch it so soon!)