Tim Bray has a gem of a post that I just have to quote:
A Really Satisfying Feeling
Going through a bunch of source-code files and and, one by one, removing the dozens of “print” statements that let you focus in tighter and tighter and tighter on a really obscure problem until you could finally see it. Debuggers are OK, but when the going gets tough, the tough use “print”.
Lo, behold: The tough use “print”! Though, I am not alone :)