I've been playing on my Index without my glasses initially, as I was waiting for prescription lenses to turn up. Alyx looked great (though a bit blurry of course), but with the new lenses inserted it looks incredible. Easily some of the best VR graphics I've seen, and it runs so smooth. This is the first title I've seen that gives Oculus exclusives like Lone Echo serious competition in terms of graphics and immmersiveness and overall polish.
Once I've played through on the Index I intend to try playing through on the Quest (hopefully wirelessly using Virtual Desktop Steam VR streaming) for comparison.