Style a GXT Grid Row Using GridViewConfig

At work, we're using Sencha's Ext GWT library for much of our GWT based application. A few weeks back, I needed to implement some functionality to style rows in the grid based on information in the model data. After struggling through a number of poor approaches, I found GridViewConfig, which sorted things out nicely. While the logic for determining style in our app is more complex, this simple case demonstrates the principle:

Tho I've found the CSS side of things to be more finicky than I would have hoped: