Update: Bought a Yaris SE.
We drove pretty much every car in the class. Mazda 2, Yaris, Scion xD, Chevy Sonic, Ford Fiesta, Honda Fit, Kia Soul and Nissan Versa. At the end of the day, the Yaris seemed like the most car for the dollar. After explored used options, we realized that getting a high-mileage car used isn't really a great idea. The mileage totals on those cars was staggering. $17K for Prius with 100K miles? $14K for a Toyota Corolla with 80K miles? Just not that great.
I really wanted to love the Chevy Sonic. It was a solid car, but just lacked the overall style of the Yaris to both of us.
Toyota had a cool deal of a $1000 rebate for recent college graduates. My wife happened to have a picture of herself holding her diploma from a couple weeks ago. Nice.
The Mazda was the cheapest, but definitely felt like it. Loud and rattly on the highway.
The Fiesta was the most expensive, but lacked the polish of a $20K car
The Chevy was just "eh." And for basically the same price as the Yaris, it was an easy choice. The built in Michigan factor wasn't enough to over come general lackluster design.
-chef