TLDR; I recommend the Pinephone if you are an experienced Linux power user who likes to tinker. It's early-adopter hardware and isn't ready for the average user yet.
At some point in the middle of 2021 (I don't remember exactly when) I purchased a Pinephone[1] that came preinstalled with Manjaro ARM and Plasma Mobile. I played around with it a while, learning desktop applications like Konsole and even some games like Quake and Bugspray were both relatively easy to install and run; Their optimised-for-desktop design sometimes got in the way, although it wasn't unusable by any means.
After a few days, I felt Plasma Mobile was a bit sluggish and Manjaro a bit heavy for my taste. I decided to try out postmarketOS as it is based on the much lighter Alpine distro and has SXMO[2], a mobile desktop environment designed primarily with power users and the Pinephone in mind, using X11 (and now Sway) and a handful of shell scripts, SXMO is a surprisingly snappy and usable environment, albeit with a slight learning curve as it doesn't use the traditional application grid and monotasking design, instead using a custom launcher using dmenu/bemenu and tiled window management with dwm or Sway. Almost all of SXMO's features are available over SSH too, so you can write and send SMS messages on your desktop computer or share the phone's data connection with it.
After around 6 months of use as a daily driver, I find the Pinephone with postmarketOS very usable. Calls are sometimes a bit muffled and SMS messages sometimes post 2 or 3 notifications, Firefox struggles without OpenGL 3 support, although it performs much, much better on versions <= 91 with WebRender forced off. Unfortunately, versions newer than 91 have removed the ability to use the 'basic' Gecko compositor. Megapixels, the default camera application for SXMO, obviously still needs some work, but it is usable, if a bit grainy and undersaturated. Games aren't one of the Pinephone's strengths with its relatively weak and ancient Mali 400 GPU, although if you have the convergence dock you can connect a mouse and keyboard and play some older games. The Alpine and postmarketOS repositories have a few games such as Doom, Minetest, some emulators, and the Gnome and KDE game suites.