Are ASCII diagrams within source code worth the time they take to create?

I could create a bitmap diagram much faster, but images are much more difficult to in line in a source file (until VS2010).

For the record, I'm not talking about decorative ASCII art.

Here's an example of a diagram I recently created for my code that I probably could have constructed in half the time in MS Paint.

          Scenario A:

                                       v
         (U)_________________(N)_______<--(P)                   Legend:
          '     /             |                    J = ...
          '    /              |                    P = ...
          '   /d              |                    U = ...
          '  /                |                    v = ...
          ' /                 |                    d = ...
          '/                  |                    N = ...
         (J)                  |
          |                   |
          |___________________|