It does seem fairly usable already. I'd say it's going to be viable as a primary workstation sooner than later, but things like polished GPU drivers will take more time.
There are other ARM machines as well, that run Linux more easily, but those aren't as high-performance yet.
Some acceleration for sure is necessary, though things like video acceleration (that belong in the set "polished GPU drivers") are quite secondary. Linux is a good example of that, accelerated video decode is still quite rare and finicky.
There are other ARM machines as well, that run Linux more easily, but those aren't as high-performance yet.