I've got one of the Granbergs, I like it, I will hand file once or twice then use Grandberg to get my angles and tooth length correct ,I bought mine new in box and lightly used Grandberg bar mounted file guide for I think $15.00 bucks at yard sale couple years ago.
Took a few uses to be able to set it up quickly and correctly,after 2 or 3 uses I can sharpen chain almost as fast as hand filing.
If I hand file only I always get one side shorter and different angle, so I've always took chains into town to get sharpened after I hand filed them a few times,its got so dang expensive to get chains sharpened any more I figured for 15 bucks why not give the Grandbergs a try, I doubt I would of paid much more for Granberg sharpener before using one,but now if it would get lost,brocken or stolen I'd replace it with another one.
A electric bench sharpener would be nice,but I like the portability of grandberg. I havnt used bar mounted file guide but it should work.