It helps greatly in pinpointing a very distant ancestor and they always inform you when another "Wicks", for example, has had the test and if they match. Then, you can contact that person to get their "tree" and see how it fits with yours. We've had great success on the KEMP, TERRY & LONG ancestors. It's just a new added tool to help genealogists and they don't use the DNA for anything else.
My James WICKS said he was b. in Schnectady, NY, ca 1807, & m. a Mary who said she was b. in Otsego Co., NY, ca 1806. They then moved to Livingston Co., NY, & from there SOME came to MI, including James but I find no Mary. NY is very difficult to get info from so I thought perhaps the DNA might shed some light on some ancestors.