I finally got around to opening the steamdeck today. I recommend doing it with the window open and a fan because the smell of new electronics is strong as hell and it takes many hours for that to outgas. The reason I am making a point of this right off the bat, is because I know some of you will feel sick from new electronics smell and blame it on the screen. So have ventilation as a best practice. The case for it is also very strong smelling, I have it outside and it'll stay outside all night too.. needs to outgas. Has that strong new carpet smell.
First impression, the screen is smaller than I expected for some reason. The backlight is VERY blue (about 8000K). It does have a customizable night mode setting for the interface so you ca make it warm, though that doesn't apply to games themselves, you would need to create a custom colour profile and add them to the game as a 3D lut or something--some people have done this. The colour gamut coverage of the panel is not high (68% of sRGB). Not great, not terrible but combined with the anti-glare, the general look is a bit dull and unsaturated. I didn't observe flickering, and while I know some of you will complain about strain, part of it is because it's blue and the pixels are a different size than you're used to. The screen I have is the etched semi-matte one (512 gb model).
I haven't played games on it yet, I think the device is useable but there is some degree of getting used to it. Haven't connected it to my monitor yet.. it comes with a KDE desktop but you need a dock to connect to an external monitor and I don't have one. Some people have installed Windows on it, but driver support for it is not fully present yet.