This is the one of the many Holy Wars that programmers engage in. Beware of the power of the dark side.

For me, I put the complexities in my data, document the data and call it a day. Sometimes it's necessary to provide a road map for large programs, but any more than a couple of lines of comments for each function means that I'm doing something wrong.

The one exception to this being places in the code that I know are going to have to be changed: a future programmer will have to meddle in it, and a config file would be overkill. These I block out to be obvious, and then document each and every single thing carefully.