I realize this trimmer is a pretty radical departure from the normal 'lathe' type trimmer in as much as a machine tool (in my case one of the engine lathe's) provides the motive power instead of your arm or in the case of a power adapter, your power screwdriver, however..
Repeatability across a group of cases is much better, typically 0.003 and the case mouth comes out square in relationship to the body because the case actually locates in a chamber specific machined insert.
Additionally, it takes up much less room on your bench (goes in it's little shipping box in a drawer) and cutters are dirt cheap (typically a 2 or 4 flute centercutting mill (import) is about 4 bucks from Enco.
Dale recommends a cordless drill (in your left hand if you are right handed or right if you are a lefty) and that works fine too.
What most impresses me about this trimmer is it's fast (trimming can be drudgery with a lathe type trimmer, I know very well) and there is no side force applied to the case which is typical on a lathe type trimmer, no matter what brand it is.
When Len posted this review, I didn't know who 'Daryl' was either. Guess thats me.
No brother named Daryl either, at least I don't think there is.........