I did the Ancestry.com one last year. The initial result was surprising. Not geographically, but the percentages. I had always thought I was more German than Scandinavian, but it said I was more Scandinavian. Then they updated my information and it's pretty much spot on what I thought I am. The more people who take the tests, the more accurate it is.
As a member of Ancestry, they have a beta program called Thru-Lines. It matches your DNA with the names in your tree. Instead of just a long list of your DNA cousins and not knowing exactly how they fit into your tree, you can use Thru-Lines to find out which branch that person is in. I've found that the most helpful. On my husband's side, his paternal grandfather Harvey was a mystery. We had always thought he was born in Pennsylvania, but then we found a possible match born in North Carolina. With Thru-Lines, I was able to confirm that it really was him in North Carolina by having a DNA match with a descendant of Harvey's sister Daisy. So that was a huge break-through since we finally had Harvey's parents' names.
My mom gave me the 23 and Me test at Xmas. I finally did it and sent it in on Friday. I added the medical info since she just gave the ancestry test. I'm eager to learn if it's very different from the Ancestry test and what the medical info says. Hoping it won't take too long.