I believe I have an answer to that question, but I'm not certain I can explain everything that it entails. To begin with, good finishing work on lugs actually starts early in the framebuilding process as good preperation of the lugs prior to assembly of the frame. Since you haven't asked what is "excellent or exceptional" finishing work on lugs I'll spare you my opinions on that. Also, I suppose who is defining "good" finishing work will make a difference. I can't tell you how many hundreds of time in my life I've heard people say something like "wow, the lugwork on that bike is beautiful" while looking at a completly out of the box set of Nervex pro lugs on something like a Peugeot, Raleigh, or Paramount. There isn't a single stroke of good finishing or prep work on those lugs whatsoever. I never ceases to astonish me as to what people can and can't see when looking at a bike.
I would call "good finishing work" a bike that has at least a sharp and square lug edge, without any factory or other imperfections in the profile of the lug, and a clean braze job. Running over the lugs after brazing with emory cloth will give the lug a better appearance that just leaving them alone, like you will see on any IC lugged factory bike from the mid 70's to present. Most modern framebuilders and factories are right in there between OK and good depending on wheather they have taken an extra 5 or 10 minutes to run emory cloth over the castings or not. Almost everything you will ever see comming from high end factories or custom builders worldwide qualifies as good by that deffinition.
If you actually want to know what above adverage to excellent and exceptional lugwork and finishing is then let me know and I'll explain my deffinition of that as well. Only a small fraction of a percent of frames ever built, and especially these days, exhibit the characteristics of exceptional design and finish. Talk is cheap and many lay claim to such; but personally I believe the numbers are so small as to be staggering. Most have either given up or never wanted to or knew how. Learning to really recognize the qualities that define exceptional frame finishing probably would require one to have a LARGE selection of frames in front of you at once of various degrees of finish, and someone to actually knows a lot about it to point out and guide you to a deeper understanding and appreciation of the craft.
Hope that does a little bit to answer your question.
Brian Baylis La Mesa, CA Never done a good job on a lug in my life.
I guess the subject line of this thread is what I am trying to find out.
Clueless in Palo Alto, CA