My parents did DNA tests.
For me part of the interest in going through my mother's links involves backing up the paperwork, because it might suggest I've gone wrong somewhere if one place is void of matches but also just because it was written down doesn't necessarily make it true! Case in point, my grandfather has a birth certificate naming the man my great grandmother left her husband for, but DNA has confirmed conclusively that her husband was the biological father (something we already knew from family resemblance). Non-Paternal Events can and do happen.
Another thing is tracking down people where there is a lack of paperwork. My great great grandmother was illegitimate with her father not named. With the DNA, we've narrowed him down to one of five men and while we might never know which one did it, I now know the family he came from.
One last thing, as an aside, is helping other people. When you get a group of "shared matches" and you've identified where some of them are related to you, you can say that so-and-so must be related via the BLOGGS line somewhere and you might be able to solidify someone else's research.
