I had to use debugger on regular basis in Java and C++, but never in Python, because Python programs end up being much simpler.

Also, you can simulate large parts of the program in IPython and not only find what the problem/bug is, but solve it right there and copy the solution back to the original program.

Totally agree. A great debugger can be a godsend. It amazes me that for the longest time you can not see return values when debugging in Eclipse. https://bugs.eclipse.org/bugs/show_bug.cgi?id=40912

I prefer C# for "scripting" (faster iteration) - but I agree that debugging facilities are a must. I've sunk a lot of time adding basic debugging facilities (basic things like call stacks on errors, dumping variable contents, etc.) to scripting solutions that didn't have them.