"In the latter case its little more than taste, and I see that Pauan is doing the same thing."
The reason I numbered them was just to make it easier to navigate the code. As a user, if you see "01 nu.rkt" you know it's loaded first, and that "02 arc.arc" is loaded second. And each one builds on the stuff defined previously, so you can read it in a linear order.
I only did that for the stuff that's automatically loaded when you start up Arc. You'll notice that the "lib" and "app" stuff is un-numbered. And I don't expect user-created code or libraries to use numbers! So I definitely don't take it as far as wart does.