The coefficient of determination (R2), and its "adjusted" counterpart, really don't impress me much! I often tell students that this statistic is one of the last things I look at when appraising the results of estimating a regression model.
Previously, I've had a few things to say about this measure of goodness-of-fit (e.g., here and here). In this post I want to say something positive, for once, about "adjusted" R2. Specifically, I'm going to talk about its use as a model-selection criterion.