I have had numerous possible breakthroughs, stymied by the fact that Ancestry provides no way to properly verify their data. So IF I could convince a dozen strangers to upload their raw data to GedMatch, it is possible that I could prove the parentage of my 4th great grandfather. Numerous genealogists, much more qualified than I, have been searching for years and not been able to find documented proof. We have tried through Y-DNA and have "proven" several sons but do not match any of the people with the same surname who immigrated to America at the same time. I have numerous POTENTIAL autosomal matches to a possible line, but their one testee has Y-DNA totally different even to the haplogroup. Either the Ancestry matches are wrong, or the other person has a NPE he doesn't know about. Without seeing the chromosome match-up, I have nothing. Our only hope is on GedMatch - maybe someday.
So the potential is there. Ancestry may be thrilled with their "better mousetrap" but until I can verify the matches myself, I will continue to urge people to test at the other two companies.