I have rank 1 windmill, and I'm not at all as satisfied as I thought I would be. I don't regret getting it though, and that's not to say i'm not happy with it either, but I say rank 1 not the "good enough" rank. Rank 5 is "good enough". Rank 9's....ok, but I just wouldn't be able to rely on it as a means of attack. Rank 9 is more for an escape button.
I suppose it's my fate as a Dark Knight. Soon, I won't even feel any remorse for my actions.