I find myself using the multitool a lot on jobs, more and more often. It does a great job on cutting drywall, wood base, all sorts of things that occasionally have nails in them. The blades are pretty expensive and this last job I dulled a couple of them.
I started out placing an order for more blades and it occurred to me to try sharpening one of them. The Harbor Freight dished half moon blades I filed with a triangle needle file, took maybe 5 minutes. The Versatool bimetal blades (nice blades, by the way) were too hard for a standard file, so I used a Harbor Freight diamond triangle needle file. A stroke or two on each tooth and a couple minutes and it was good as new.
The blades have a slight amount of set to the teeth and I didn't worry about it or filing from both sides, I just clamped them in a vise between two scraps of wood and had at it. They work good as new.
I figure I saved more than $50 in a half hour.