Hi Blue,
Myself and 3 erstwhile same surname possible X-times-removed 'cousins' did DNA tests last year. All four of us have confirmed long-term roots in Ireland going back beyond 5 generations and while the results were interesting to an extent they were overall disappointing.
I was a close match [10 out of 12 'markers'] with a 'cousin' in the US but nowhere near a match with the other two; one in the UK and the other in Ireland. The close match indicated a common paternal ancestor between 1000 and about 1,500 years ago! There's no way we can find out who he was and where he was from, although the DNA does point to where the bloodline originated from 2,500 to 25,000 years ago, possibly via the Basque area of Spain.
However, I had a perfect 100% match with two people in the company's database; one in Wales and the other in New Zealand! The Welsh one wished to remain anonymous [no email address or contact details] but I was able to contact the NZ one. Turned out his paternal g.g.father arrived in NZ from Essex about 1875. His surname, Hunter, had never appeared in any of my lot. I have been able to find his family back in Essex in 1861, 51 and 41. From ages it would appear the Hunter g.g.g.g.father was born about 1770/75. That period is the same as when my g.g.g.father was born in County Clare, Ireland. According to the DNA company a 100% match means a common ancestor between 500 and 1000 years ago.
So basically, despite the hype, the DNA test only told me that the people I wanted to be my lost cousins from a 100 or so years ago couldn't be and that sometime, over a 1000 years ago, there was a man who became a g.father [to the nth place] to both me and the lad from NZ!
I was disappointed in the lack of accuracy in 'event' timelines and it reinforced my belief that surnames can be purely accidental. After all, it isn't that long ago, in DNA terms, that surnames didn't exist as such. You were known by a first name plus a trade and/or place name. If my Irish ancestors did, as in family lore, originally arrive in England with William the Conqueror in 1066 and then Ireland in the 13th century they would have been merely Tom, Dick or Harry the cooper, smith, archer, Hunter etc, in the service of a Duke or Sir Somebody.
I've learned that the basic DNA test compares from 12 to 15 so-called 'markers'. In order to get accuracy in relationships down to the first cousin level one needs comparison of over 30 'markers'. And the more markers, the higher the cost. It isn't as easy as CSI and the like make it look!
As far recommending a company I went with Oxford Ancestors in the UK
http://www.oxfordancestors.com/
I didn't go with Anc in the US because a Wirral friend of mine who did found himself inundated with emails from potential long-lost 'cousins' from all over the States who had a 95% marker match. As far as he knew he had no emigre relatives anywhere!
Brian
[whose surname could have been Cooper, the family trade though 4 generations!]