Another new S-12 owner here.
Gregg is a great guy and a gentleman, and it was a pleasure doing business with him. And it was a spectacular unexpected pleasure to get an all-too-short look at his museum. I was absolutely stunned, you walk in the door and... Whoa, I would never have guessed the house contained such a place, and it's far more jaw-dropping in person than in photos. It's possibly the most spectacular stringed instrument museum I have seen, and certainly the only harp guitar museum I have ever seen. I hope someday he moves it to a public location where visitors and especially musically-inclined kids can see it, it is a very special holy place.
I've spent all of 45 minutes playing the guitar, but some impressions of my own.
1) The guitar is indeed smaller than I expected, not a monstrosity, and even in it's wooden case it's no more effort to lug around than any other guitar.
2) It sounds wonderful! The tone is very warm and subtle, and responds to small changes in how you pick the strings and where you pick them. It's a well-made all-wood (spruce top, mahogany elsewhere with rosewood fingerboard) guitar, and it sounds like what it is.
3) It plays very well. I too am used to the 1 7/8" nut width, and I like the action higher than some, so it's perfect for me. The intonation is fine, and the tuning wandered a bit until I had played it a bit, I presume the strings hadn't been worked very hard before.
3) Hardware is all good, fit and finish is good but not comparable say to my 456. I expected that, not a big deal. Some of the fret edges are a bit rough, but I had to look for it to notice. The only thing that stuck out, just because I'm not used to it, is that the neck surface is also open-grain and not super smooth. Not a big deal, just different.
The harp guitar part, will take some time.
I'm a hybrid flat picker, so to really make use of the bass strings I'll need to change my style when I'm playing this guitar. I ordered some thumb picks to experiment with, that might be all I need. But it'll take some time.
All in all, big thumbs up on the whole transaction! Hopefully by the time the harp guitar gathering comes to CA, I'll be able to play the thing reasonably well and be able to pick up valuable tips from other players.