Mike Appel is probably not well known outside the midwest as a framebuilder, but you've probably seen his work without realizing it. Many early Trek frames out of the Waterloo barn were built by him. After working at Trek both as a builder and a painter, he started building on his own in Madison.
I don't often see Appels for sale on the used market. This one is priced much more reasonably ($400 f/f/hs, $600 complete 7-sp group) than what I've typically seen.