This was a belated holiday gift to myself - that Santa knows just how I like to use gift cards. Anyway, I've wanted one of these for a long time, but just never wanted to spend the money I guess. I grew up and spent most of my adult life filing by hand.

Quite a few years ago I got one that mounts on the bar and runs on 12V. It's a similar design to this, just a bit smaller diameter disc. I'd gotten to like that one quite a bit, except for two problems: 1) you couldn't do up say 2-3 spare chains without swapping one off and another onto the bar, and 2) it was not very easy to transition to different stones for smaller gauge chains.

With my boys pitching in now, we have four saws just here at the house ranging from a 12" 'micro' (1/4"/6.35mm, 64) electric a 3/8" 73LGX on the bigger saws.
Anyway, this thing is great. I paid a bit more for the hydraulic clamping, but it really makes it quick. When you lower the cutter-head it automatically clamps the chain, so you don't have to keep clamping and unclamping at each stop; just advance the chain, sharpen, lift, advance sharpen, lift...

I have three stones, and the thickest (3/8") I have dress at 60 degrees for cutting the rakers, so it does both with easy. I think my days of hand filing are over.