Cool! I should also add that I've found playing power chords with the pinky gives me some more room for playing other chord shapes.

For example, if you start with a C power chord on the 3rd fret, and you drop your index down one fret to B you now have a 2nd inversion of a G chord (notes B and G, with B on the bottom). Totally common move in punk and alternative metal. Harder to do if you're using index and ring. Although index and ring is easier if you're going to add the pinky on and do an old rock n roll / blues boogie pattern.

-Carl.