I have had good luck testing my DNA. A little bit too much luck, as a matter of fact, with well over a thousand cousins on each of the two services I used! Southern genealogy is even more complicated than I thought it would be.
I have on occasion been matched with a second or third cousin to either myself or my grandmother and been able to figure out the connection. Sometimes this can be very helpful to my research. If you think you may be related to us, feel free to look me up on Ancestry.com (kbmidura) or Family Tree DNA (Kelly Bembry Midura).