Wow so much pessimism in this thread! I love 23and me and bought it for my girlfriend and parents too, they also loved it!
I like that I found out I'm 5% Asian and .1% Mongolian - it's a fun parlor trick to tell my friends I'm PROBABLY RELATED TO GENGHIS KHAN
My girlfriend is descended from many different cultures. She really liked seeing to some degree what percentages she was. Yes, we know it's not super accurate, but it gave her an idea.
We compared results on some of the tests, like proclivity to be addicted to caffeine, which were surprisingly accurate.
I wanted to know more about my ancestry so I had my parents get tested. I think it's really valuable to not only validate my genetic data, but also to see if it matches up with theirs/if they can provide more detail. I also have a hope that my future descendants will benefit from having this information on file (yes tinfoil hat peeps, it does also mean that the Trumpborg will be able to target them).
Hope that helps!