Couple of hours in on Steam Deck, and this is really not optimised at all well for it. After a bit of fiddling, I'm happiest with dynamic 800p, FSR2, 30fps at medium settings, but the frame rate is getting drops still seemingly at random
There's also a bug that crashes the game if you try to move the map around, so hopefully that gets fixed soon.
Weirdly though the game seemed to be having rhe worst time early on, with a couple of hard crashes that required a system reboot in the first lift, until I jammed Isaac on a corner so as little as possible was happening on screen.
But since then, almost no stutters, mostly locked 30fps, decent image quality throughout. Evening the start up EA splash page that froze the first time it loaded is smooth now.
Hopefully this gets some patches and SD optimised updates ASAP, as it absolutely seems to be a problem with the software, not hardware.
One last thing is that having rhe option for gyro aiming makes combat a hell of a lot better. Quickly and accurately blowing off limbs is so much easier without having to rely on sticks.
Overall though the game is fantastic, although year, the obvious pandering to modern audiences of twitter weirdoes is ham-fisted and breaks immersion, but the core game is still as good as ever.