As far as the Heatherly's go both of them have been in the hobby for hundreds of years (just kidding) but seriously those two guys have been around forever and they are by far two of the best guys you will ever meet in the pinball hobby.
I am lucky enough to know both of them personally and live within 15 minutes of both of them (actually kind of right between them). I don't see them often or even talk to them all that much but I can say 3 things about them. First off they are both class acts, second in the 7 years I have been in the hobby I have never heard a bad word about either of them, and lastly both of them are in the pinball hobby - not the pinball business - so they both fly under the radar a good bit unless you really know who is who in the hobby.
Both Bill and Dan do fantastic work and I think you could put their restoration work up against anyone in the hobby or business. Both of them are very successful with their "real jobs" and both are truly in the pinball hobby. If you are ever in Central PA and can hook up with either of them you will be blown away with what you see. The pins in Dan's "Barn" are as nice of a collection of restored machines as you will see anywhere in the world.
As far as your guys that have never heard their names before that is because you live in a "bubble" here on the chat rooms and don't know who some of the best guys out there really are. You just know the "flavor of the month club" everyone here talks about.
One thing I will tell you for sure is if you ever saw either Dan or Bill's work you would have no doubt they are the real deal. I feel honored to have both as friends & neighbors.