Going back over my screenshots, I found something odd when looking at the hard drive info panel.

Leopard:
Capacity: 279.14 GB
Available: 46.33 GB
Used: 232.81 GB

Snow Leopard:
Capacity: 299.73 GB
Available: 58.28 GB
Used: 241.45 GB

Now I'm even more puzzled. Why did my drive capacity jump up 20GB? I didn't pay close attention to my Mini to see what it reported.