Downloaded on both of my Essentials.
There's little things used in 8.1 that are missing that I used every day. Such as, if I have an alarm set, I can pull down the notification panel/quick settings tray/whatever it's called and see the alarm there and tap it and be brought to the alarms page in the clock app. That's gone in P. Also, I keep my display brightness set at 25% which is plenty bright for me. Now in P, I have to crank that up to 40-50% to achieve the same brightness as 25% was on 8.1. I have and always have had adaptive brightness off. Also going back to alarms, if I have an alarm set, it does not show on the lockscreen or on the ambient display like it did in 8.1.
Things that are bunk in my eyes so far: Clock on left side is just screaming iPhone X and doesn't need to be there. Greenish icons in quick settings looks like an afterthought. Blue was much more appealing and fit in more with the overall theme of things. Notch settings, are they gone or am I missing something?
I'm sure there's more but this is just after playing with it for 30 or so minutes.
Perhaps usage over time and I'll get used to stuff.
Device seems more fluid and faster even though it was fast beforehand.