I heard it messes with mozilla firefox
It’s a Nvidia driver bug, so if you’re not on Nvidia you should be good.
Im getting slight fps drops that dont seem to relate to the steam fps counter.
You could try enabling mangohud with the full config. From steam launch options:
MANGOHUD_CONFIG=full MANGOHUD=1 %command%
This will give you more detail than just FPS, although if you don’t still have your old setup it would be challenging to compare.
I’ll add I installed it on my OLED deck, and no obvious issues stand out. Chucked nix on it with the Determinate Nix Installer and deployed my Pipewire EQ and vkBasalt configs without issue (and without some of the audio output issues that SteamOS introduced with the 3.5 update). Oh and vkBasalt comes installed OOTB, which solves some maintenance annoyances with keeping it working on SteamOS.
Steam game mode UI feels slightly snappier, perhaps down to using the BORE CPU scheduler (but it could be placebo of course).