It's a very cool concept but it needs to be fleshed out a lot to make it worth the purchase price. I would say that given the lack of diversity within the exercises that it is not a very effective learning tool in its current state.
I liked:
The drill concept seems like a good way to learn quickly
The timer keeps track of your progress
Instructions are concise
I didn't like:
Not very many exercises
Doesn't cover all of Vim
Not enough different tasks within each exercise: typically it is 1-3 tasks that move to different line numbers.
Doesn't keep track of your speed so you can't see if you are improving
My experience was pretty underwhelming tbh. I've been JUST BARELY getting started learning vim, and while I am a programmer, figure I'm as good a learner as the next Joe Blow. That said, I already knew pretty much everything in this course. I'm not kidding, I knew everything listed in all of the lessons. I think this might be a good immediate starter course, but I think it would be a lot better if it were less pricey.