Perego is a researcher with the Sorenson Molecular Genealogy Foundation. The Foundation was begun by James L. Sorenson, a billionaire Mormon businessman and philanthropist. Perego presented his research at the 10th Annual FAIR Conference. FAIR is an acronym for Foundation for Apologetic Information and Research, a scholarly organization that defends Mormonism. The text of Perego's presentation can be found here.
The Deseret News article entitled, "DNA shows Joseph Smith was Irish" is easy reading and explains quite well how the research was conducted and the conclusions reached.
Niall of the Nine Hostages, Irish royalty, is a likely ancestor of Joseph Smith. I wonder if his temple work has been done yet. Knowing Mormons, it probably will be soon if it hasn't already.
Perego also debunked the conventional wisdom stemming from historical research that certain children such as Moroni Pratt, Zebulon Jacobs and Mosiah L. Hancock were Joseph's children. They weren't. Josephine Rosetta Lyon is still the likeliest candidate for being Joseph's child through a polygamous wife. The research won't be done for another year. There are about 120 DNA samples to analyze before results are in.
So, what does all this mean for Mormons? I'm not sure it means anything. Finding no polygamous children of Joseph Smith does not necessarily mean he had none or that he did not practice polygamy or sleep with some of his polygamous wives. He certainly practiced polygamy and he certainly slept with some of his wives. I don't think a rational Mormon can claim otherwise.
It is just interesting that no polygamous children can be positively identified, yet.