Well, I have to use OpenGL for my development, and it's a giant state machine that works mainly via side-effects. It's notoriously frustrating to work with, but that's life. I realize not all code works that way, but I'd bet the majority of code does. So I stand by my statement that it's a terrible way to debug, maybe with the caveat "unless you can work with only pure code and no state."
Well, I have to use OpenGL for my development, and it's a giant state machine that works mainly via side-effects. It's notoriously frustrating to work with, but that's life. I realize not all code works that way, but I'd bet the majority of code does.
I suspect your sample is a bit skewed.
The Smalltalk class library wasn't stateless. It certainly wasn't pure. Really, code only has to be "pretty good" for such techniques to work well.
