I cannot possibly overstate how amazing this is, given everything else valve is doing to make compatibility layers for practically anything.

This can attack Meta's near-monopoly on VR incredibly effectively. All those games made for the Quest? Pop 'em on either your higher-power PC, or directly on the Steam Frame, and it just works, very low effort to port, and you can squeeze more performance out of them if you're playing tethered.

Want to use an Android app on your PC rather than your phone? Done. Linux suddenly becomes much more useful to you on its own.

Being able to run Windows applications on Linux was just the start of making Linux more usable, and giving people more choice as to what software to use, but this expands it to an even larger scale. Simultaneously, this could mean some developers make things for Android that they otherwise would have only made to run on Linux, meaning Android users get more (likely open-source) choices too.

There's a metric fuck ton of apps that I wish I could use on Linux, but are only easily run on Android directly. (Yes, I know Waydroid is a thing, but it's been a pain to set up and use for me and many others. Valve has been pretty good so far at making sure things "just work" as best they can.)