[vintermann]

Best case scenario is that you can answer a ton of historical questions that you wouldn't have a chance to otherwise.

I'm currently in the process of figuring out where my most distant known paternal-line ancestor came from. Took a Y-DNA test, found a very distant all-male line cousin who was open to taking a Y DNA test (because he had already taken one at 23andMe, I knew the odds were good that he would be OK with it - the 23andMe test also had enough Y information that I knew it was likely we both descended from the same man).

His first results came in yesterday. In another couple of weeks, when his Y SNPs come in, we'll know which of my ~10 private mutations (ones no one else has been found to share) we have in common, which will in turn put better time estimates on our distance to other testers in our part of the Y-tree.