I'm afraid I eventually gave up on reading all the preceding posts. Like almost everyone on here except the most meticulously documented / royals / or even happy fantasists at the other extreme, I know that there are some "known unknowns" in my tree. Almost all on one side head clearly and neatly back to mid 1500s, not even many "hasty marriages" that may cast interesting doubts. Other side less certain, but how would DNA testing help me with this issue, for example: Two lumps of Irish ancestry, but where in Ireland not known, on that side. DNA testing may well say "Irish X%" - but it wouldn't tell me exactly where, or, even more important for family history chasing, which Irish surname came from which bit of Ireland, would it? Perhaps if I had ancestors teeth, testing those to see how the enamel had developed as the person grew up may help?
I'm under the impression that Male DNA is preferable - sorry, no male relatives left on line, so that'd not be a goer.
The cost is mentioned often - is the result worth the cost is something only the seeker can evaluate. I have heard often that different companies produce different results from the same person - and that leads one to wonder about either the accuracy of the analysis, or the probity of the firms involved.
The USA has by the very way it developed, highly diverse ethnic mixes, so that may well be why the main market is there. Many US citizens seem almost pathetically keen to discover Scottish ancestors, or, more recently, Irish seems to be fashionable, too. There's a good market there, perhaps DNA can select an appropriate tartan?
Perhaps it is the gentle process and progress of the piecing together of the history of one's own family, its movements, social developments and personalisation of the bald record that interests many of us more than seeking an exotic ancestry? Some in my wider family have been told that there is Nordic ancestry - and typical colouring, and build even up to a generation ago would bear this out, but we'd never know if it was Sigmund Sigmundson, or Magnus Boldtooth, or whoever, would we?
I'd not have even looked at this without Trystan's "prompt", but I'm not really at all interested in it as an area. Like many others, I'd rather spend my pennies (or bawbees, or kroner, or whatever) on documentation of the trail I'm following.
DNA research is a fine thing especially in medical areas, I'm not knocking that. But - does it really help in this hobby? - Not massively, in my opinion.
Sorry if this load's not been highly useful or relevant, but - done it now.