It's surprisingly boring tbh. Most things, including all the gamepad stuff, work as expected out of the box. It's quite performant and could easily replace a desktop with the dock, but for portability a laptop makes more sense. I'll keep using Steam OS on it, because I don't have a use case for arch on it atm.
~~please ignore smears on the screen~~
I just ordered a steam deck but I am not planning to install arch on it tbh
SteamOS is basically an immutable distro of Arch anyway so you're not missing out on much. Friend of mine who uses Endeavour did not like that because it means he can't use the AUR, though he missed the point on why SteamOS had to be immutable in the first place.