The first time through the early access I played with fairly generated stats, but the second time through I just set everyone's to 18 (or 19,20 with racial abilities). I figured I'd related my experience for anyone who was thinking about doing it.
1) I still failed rolls all the time. Because of course you will. A +4 isn't all that different from a +3 or even a +2 when added to a d20. It's better, but not so much better that you won't still feel the pain of failing to hit a goblin with 1 hp left despite having a 20 str and advantage. I know the math, but I was still expecting to feel like I was crushing the rolls alot more than I actually did. So essentially, despite having maxed stats, I didn't feel overpowered in terms of how often I succeeded. It was about the same, with a mildly better difference when there was one.
1a) still, I could use my whole party to pick locks, because they all had at least a +4 to the roll, and if my two lockpickers failed, I usually rolled high enough by the time my mage tried it. Also, switching to ranged weapons with my cleric or melee weapons with my mage were legitimate options. So while characters did about as well at what they were supposed to be able to do, they could also do anything else as well.
2) The bonus to damage felt a lot more that I expected. Having a +4 or +5 felt a lot more than a +3. Knowing that my minimum damage was 5 or 6 (or 7 with sneak attack, etc) made me feel like I was hitting harder. I think this is largely psychology, but somehow that +1 to damage to damage felt like it put in work, while the +1 to hit seemed nice but forgettable.
3) Hitpoints, I had a lot of hitpoints. It was nice. Made me feel bold. I still got knocked down from time to time, but since my mage had an extra 8-20 hp I knew he could soak an attack of opportunity from a goblin or two.
4) 18 strength means you can load up your mage with all the inventory. I didn't run into carrying limits, and I HATE carrying limits. I know why they're there, but they are not why I'm there, so I didn't mind them being largely diminished.
All in all, I liked it. It wasn't overpowered, but it was definitely empowering. It made a difference, but not too much. I felt my characters could do more, endure more, but were still on a sort of fair playing field.
I know that a purist wouldn't go for it, and I'm not convinced I'll do it for my actual run when the full game comes out, but I've got no regrets for using it for the playthrough I did.
Has anyone else tried it?
Typos happen. More so on the phone.