And let me say that I really do like that this works in D. I can't imagine doing anything like this in C++ (which is what I used primarily in the past).

The only reason I joke about it being useless is it really only supports vectors of length 2 or 3 (technically 1 as well but that is not really a vector) and at that point I am tempted to say it is more efficient to just make a Vector2!float class or something of the sorts.