The Steam Deck delivers as promised, the biggest question mark with the SD is how Valve will support it over time. Previous Valve hardware has been abandoned pretty quickly since Valve as a company appears to have the attention span of a 5yo
You could argue they quickly abandoned Steam Machines, but they didn't actually make any, they were just branded PCs (so they didn't need active support from Valve), and barely any sold. They still support the SteamOS some ran on, because the Steam Deck also runs SteamOS.
It's a PC so there's no need for "support" from the manufacturers... at least on windows.
With Linux the manufacturers have to update the drivers. Maybe one day Linux will get a stable driver API?
For once Windows users spent a few days in the shoes of a Linux user.