I replaced an aging laptop with mine, and I have to say, Windows is fine on the Steam Deck. It's obviously not going to have all the same bells and whistles but performance for most games is the same and it is more flexible on compatability since it runs natively instead of via Proton.

I've been using dual boot for this and started since I got my Deck in early July last year, and a lot of the hate is really overblown. It's good if you just want to use the Deck the same way as any other computer or with applications that cannot work in Steam OS and it's a completely fine experience, and applications like Handheld Companion or Steam Deck Tools make it simpler.

I would just say that it's up to preference and need since it does need setup and tweaking, so if all you care about is playing a few games that work fine in Steam OS, there is not much reason to dual boot for Windows and Steam OS is simpler to set up. But if you want more freedom on application choices and compatability or even just to use it for more everyday purposes like any other computer, Windows runs perfectly fine on it. It will be ultimately up to preference and use case.