>Quite reliable.
Perhaps, but I have not seen much to give me your confidence with it. I recall seeing several threads here on FR in the past few months which concluded that all such studies to date have been overblown and rigged.
Well, yes, some of the stuff is both overblown and rigged. That is, when an agenda is part of the search (as with some anthroplogists who MUST show a recent "out of Africa" scenario). And, there is a reasonable limit to how far one can look back with accuracy. But, if the Celts and the old Hebrews separated about 2500 years ago, there would be footprints in the DNA that would be reasonably reliable.
As far as I'm conscerned, stranger things have happened; personally, I would be delighted (I am of Hebrew ancestry and an Irishophile!