I have somewhat similar experiences. I started by having a paternal male cousin test his Y-DNA in a Surname Project with FT-DNA. We ultimately found matches to three sons of my 5th great grandfather but no matches to similar surnames who migrated to Pennsylvania at the same time.
I tested myself with autosomal DNA from Ancestry this fall. I have numerous possible surname matches (one along with two other son matches to a person with a not so well-researched tree) but nothing consistent enough to make any judgements. I am waiting for the raw data to evaluate the matches.
I also have probable families to research for several "brick wall" grandmothers. I have found 3-5 matches to the same family for each of them. Plus I have "proven" the family of a 5th great grandfather with numerous matches to both the family I suspected and to the mother lines as well.
All in all it has gone very well