My purposes have been to confirm or disprove the lineages that the paper trails provide and to break down brick walls.
I've had decent success with the former (in many cases not documented on Wikitree, yet). As to the latter, no big winners, yet.
In autosomal land, I need to be more systematic with my approach, and in particular, to develop maps of my parents' chromosomes, before I'm going to be able to isolate matches, if my parents have any, to my most troublesome brick wall people.
My family's y-dna might eventually help me with the patrilineal line, but I will probably need more people to test before it yields anything.
I have an on/off research project to find the common ancestor my dad shares with a match on the mitochondrial side, and I feel like I'm a generation or two away from finding the MRCA, but presently bogged down in the match's genealogy and that project has been dormant for a while.
Edit: just saw you said, "don't respond both," which I guess I did. Sorry!