I've been fortunate to have been able to see him every year for at least ten years, including this past June. And I am priviledged to have had supper with him after the concerts. Also, I and my partners have had him as a live guest on our radio show. He's a heck of a nice guy, and his conversation is sprinkled with stories about his contact with multitudes of famous folk performers. (Even a couple about Seamus Kennedy!)   :-)
I got to read the first draft chapter of his book just after he started writing it.
I consider him a good friend, and if I ever decide to try to impress people by dropping names, Bill's will be one of the very first I'll drop---or am I doing that now?