So, here's the question: How does 19-EDO "sound?"
Hrm, well, it sounds like whatever instrument is used to play it, really. It's a little weird, but not too far off from the way 12-EDO sounds.
In fact, in my experience, anything you can play in 12-EDO (standard tuning for guitars and pianos and so forth) can be played in 19-EDO without sounding that different, with a couple specific counter-examples.
Since 19-EDO is best notated using standard Western music notation, you can conceptualize musical phrases the same way. If I play a familiar melody B A G A B B B rest A A A rest B C C rest B A G A B B B B A A B A G. It sounds like "Mary Had a Little Lamb." Playing the same passage in 19-EDO or 12-EDO really doesn't make much difference. Expand from that simple melody to basically any western-influenced musical piece written in one key and everything sounds the same.
The differences:
Ok, if there were no differences at all, it'd be silly to mess with all of the extra fretwork or buttons or keys or whatever. So, there are some differences.
1. Thirds are sweeter. Both the major and minor thirds (and congruently, the sixths) sound just noticeably closer to just intonation than they do in 12-EDO. Fourths and fifths sound just a little less sweet, but I think it is too subtle to really notice.
2. Chromatic passages don't really translate directly. If you play something like B Bb A Ab G Gb F E Eb D Db C B in 12-EDO, and then in 19-EDO, it'll sound different. The 12-EDO is very stepwise, and the 19-EDO is more varied. On the other hand B Bb A# A Ab G# G Gb F# F Fb E Eb D# D Db C# C Cb B, in 19-EDO, it sounds like a nifty chromatic run, but, the same thing in 12-EDO sounds like a blob of notes.
3. The "Hendrix Chord," what I was taught as E7#9 - E dominant seventh with an augmented ninth. This chord just doesn't sound right to me in 19-EDO spelled that way. But there are other chords that emote a similar vibe...
The other random thing is key changes, and, for me, at least, this is where it gets rather fun. You can blast out some fun riffs in a song in the key of A major, then have a sudden key change to Gb major and, ...whoah!
In general, I've found that every micro tuning seems to sound a lot weirder on paper than it does in reality. Even tunings that kick sand in the face of modern music theory, like 11-EDO or 13-EDO, sound pretty normal until you try to harmonize or play chords, and then it sounds more or less like a jumbled mess of nonsense rather than some sort of mind-blowing secret code to the universe.
We see a lot of people coming to microtonal ideas in search for something novel or unique, but, in practice, a great deal of the tuning options out there can be played to sound normal and usual. 19-EDO is a special case of that, sounding very consonant and generally pleasant.
Think of it like someone saying that they made a bunch of new colours. Where you were used to seeing red, orange, yellow, green, blue, indigo, and violet, now you are being shown colours like reddish-orange, lime green, cyan, and purple. So nothing really looks foreign, but there is a different palette, and you can do some different things with it.