Know it's been a while, but just noticed a post on Berg's. I bought my first on Ebay in 2013, and they have been my primary concert instruments ever since. Just bought my fifth Berg earlier today. Of over 50 dulcimers in the 26 years I've played, McSpadden is the only brand I've bought more of, and that's just because there are more of them out there.
Bill makes great instruments: even the student models sound better than a lot of "upgrade" instruments on the market. Action tended to come a little high on most of his instruments I've owned or handled, and could cause intonation to pitch slightly sharp in the upper register; lower the strings just a touch and it's right on the money.
Because he doesn't have the name recognition of McSpadden or Folkcraft, used instruments usually fetch less than half their original new price, even in top condition; making second-hand Bergs possibly the best value in the dulcimer world.