I just listened to the samples and it seems a bit hit-or-miss. Some of them still stumble over words, have stilted pacing, or just sound off in some other way (raspy-ness, speed). It seems to vary more voice-to-voice than by the quality setting.

I mean I'm sure some of these voices are fine and probably better than other AI models in terms of performance... though they are a bit uncanny valley and I still think a voice meant to sound robotic (while still having personality) is probably an easier target. I didn't notice anything like that in the samples, though I did see a couple of YT videos with a GlaDOS voice (sounding fairly accurate) that mention Piper (though I know such a thing likely wouldn't be front-and-center due to licensing).