I have not bought any guitars from Bill at Vintage Kohno Guitars, but I have talked to him on the phone a couple of times and exchanged some emails. I ALMOST bought one from him, but ended up going in another direction at the last minute.
My overall impression of him is pretty darn good. He definitely knows his Kohnos and he describes them well on his website. He answers questions quickly and gives accurate information - I never felt like he was hard selling or exaggerating to make a sale. If you are interested I would contact him, he seems to have more Kohnos around than what he lists on the web site.
I think his prices are higher than if you are sniping on Evil Bay, maybe around what GSI might charge. But then you are getting his experience as part of the package. Also I think his prices would be negotiable somewhat.
The only unknown that would stop my from buying from him is his return policy. I simply would not buy a guitar unseen if I can't return it - that's a deal breaker. I'm ok with paying shipping both ways and even a 10% return fee - I understand that. I do not know what his return policy is and the website does not say. His reverb sales are final - not a good sign.