Call me old fashion, but I can sharpen a blade using a file sharp enough you can shave with it, BUT... I'm using Fusion blades now and I destroyed one of my good files trying to sharpen my back up set. But I just found a a Diamond file set at Lowe's called Chef's Choice that does the trick for $30.
Now I can rotate my blades again. I like to rotate my blades every week to keep my cut looking its absolute best, and that way it requires a lot less sharpening. A few swipes and they are cutting paper again.
Thought I'd share my find for those of you who like to get your blades super sharp and like to do it by hand. $30 is a bargain!!!