I had mine done last year. They send you a testing kit and all you have to do us spit in a cup and mail it back. The results told me mostly what I already knew (Hungarian/French/Irish), but I also found out we have Spanish blood. I get the biggest kick out of that. A sailor from the Spanish Armada washed up in Ireland?
I am a descendant of at least one of those sailors, and it was confirmed by the ancestry.com test.
I used the ancestry test, and found the ethnic results quite interesting. They weren't quite what I thought that they would be - but have opened new channels of interest. I've been able to contact some 3rd and 4th cousins through the profiles, too. Our branch of the family had lost track of many others.
FYI - Several times recently ancestry.com has had their test 20% off online. If cost is a factor, one could keep an eye on the price for when there is a markdown.