Anyone done a DNA test and learned something interesting?

Depends on what you mean by "trace." If you take the test (which with Ancestry.com basically consists of drooling/spitting into a tube and sending said tube to them--yes, I know, that's icky), they will do a lot of the initial work--i.e., telling you what your national/ethnic genetic background roughly consists of, along with approximate percentages of each strain. Of course, it isn't free of charge, but by paying their fees, you will be provided access to many records that would probably be closed (or much less accessible) to independent ancestor-seekers. And they will anonymously and privately suggest possible relatives (e.g., "You have a potential third cousin").

In my case, it wasn't so much that I learned something new as that Ancestry.com confirmed that what I was told by my parents was largely true (and not just family legends). For instance, I had always been told by my father that his father (the grandfather I never knew) came over from Scotland in the early 1900's. Not only was that confirmed, but I also found out that my maternal great-grandmother was indeed of Welsh descent, as my mother's family always maintained. I also discovered that, in addition to many, many Scottish forebears (on both sides), I had quite a few who were Sassenach--er, English. And, getting back to my father's side, I had confirmation that his grandmother--not the mother of the father from Scotland--was born in Ireland.

So what with the Scots, the Welsh, and the Irish, I'm as Celtic as I believed--and hoped--myself to be (with the aforementioned English thrown in for good measure). Plus, I had a tiny sprinkling of French and Dutch ancestors as well, with the most exotic strain being a trace of Finnish.

One disappointment: because my maternal grandfather (a Missouri-born college professor) had high cheekbones and straight black hair--that is, when he still had hair --I always hoped he was of partial Native American descent. Nope. Same old British Isles ancestry. Oh, well. But then, as the Scottish saying goes, "We're all Jock Tamson's bairns." (I.e., "children of Adam.")