Okay, some actual feedback.
Players Roll Everything
There's a LOT of other games that go this direction, so it's probably a good inclusion. It increases player agency for Inspiration and rerolls, and they can choose what to avoid. It speeds up play since there's less math communication back and forth. And there's no chance of DM fudging, so it seems more fair. Plus the DM can focus on the story and everything else.
Surprised they didn't include a "roll to hit instead of saves" variant. Or is that already in the DMG?
Vitality
Some people really like separate pools for health and luck/energy/skill. I have some on
my website.
This is interesting as it doesn't go down separately but
with hp. But it has the standard effect of weakening character after a length of adventuring potentially making boss fights harder.
The math involved is also tricky. Effectively, for every 20 hit points of damage a character takes, their maximum hit points are reduced by 1/level. But this is less intuitive.
Custom Alignments
This is mostly advice, but is easily the best part of the article. Some good advice here.
While this article is so-so I like that Mearls is doing other things in
Unearthed Arcana than just providing new player crunch. This is what I hoped the series would be. Still, it's a bit short and they probably could have easily included some more variants and house rules. Maybe some advice on how vitality might affect the game.