Out of the box it works, including cloud saves.

The only thing I needed my PC for was to upgrade the SSD: I used my desktop to prepare a flash drive with the SteamOS image. Honestly you could probably do that using a USB adapter on the Steam Deck, booting with the original SSD.

It really comes down to convenience. It takes a minute or so to switch between desktop and gaming modes on the Deck. A lot of stuff is easier if you have a larger screen or two, plus a mouse and keyboard. And file transfers are faster over Ethernet. All of those things you can either work around with the Deck as it is, or you can use a dock or hub to plug in those extra peripherals, but it’s still an inconvenience unless you’re planning on using it docked often.