I don’t use it as a desktop replacement (I still have a windows desktop). But I do but default have my deck docked and hooked up to a TV, in desktop mode.
I’ve installed various flatpack programs, to include discord, chrome, and a couple jetbrains ides for various languages. They work great. I’ve done a couple non steam games (diablo), with mild annoyance but success in the end.
I have not used any office programs on it (as much as it’s cool to like Linux, I just think Microsoft wins by a lot there, and have no desire to get them working on Linux).
The deck itself has some power limitations, but I have no reason to think that they would translate to steam os on a more powerful machine.
So basically, it probably depends on what you want. It’s pretty reasonable. Definitely good enough for my secondary computer that blocks ads for videos on my tv. But personally, I still want a windows computer, because windows is the default assumption for most software I use.