I've always had a case and a tempered glass screen on my iphones. For the S8 I opted to go with the official Samsung screen protector along with the Alcantara case.
Love the case. A lot. Simply gorgeous and NOT slippery!
The screen protector is fine indoors, but outdoors it sucks in bright sunlight. The visibility is greatly reduced. That wouldn't happen with a tempered glass screen.
I do agree with the original poster that the S8 is far too fragile. I saw one of these take a three feet fall and practically explode. Ouch. And they just feel fragile! The curved glass is a gimmick and by design fragile.
Bring on the Essential Phone. I hope it's awesome and changes the course of all smart phone design and manufacturing.