Here's a video tutorial discussing subdiv creasing inside maya 2014. But even if you don't use maya, you may still
find this video interesting, as I feel Catmull Clark creasing should be something available in
all 3d packages.
The big advantages of creasing is lighter geometry and easier to change the hardness/smoothness of the
edges. In the tread example below, the tread with support edges has 47,400 verts, and the creased tread
has 5585 verts.