I had already written something about this earlier, but I've only been using it more intensively now. I have to say, the whole thing has developed tremendously. With a few settings in the system and in IPython, the whole system behaves almost as comfortably as a Lisp system prompt.
The integration of display system (on OS X it's recommended to set LESS to '-R' so that color information is evaluated) and editor (of course using VIM is recommended, but it also works quite well with the bbedit command line tool) allows you to work very nicely with the Python shell. On one hand, you don't have to constantly step out to quickly look at files or change a file, and on the other hand, you really get useful information with exceptions (the automatic activation of the debugger helps here).
Automatic deep-reloading too — that is, reloading a modified module while updating the contained references — helps tremendously, since you can finally edit the files directly and test them immediately without having to exit Python every time. Existing references to objects from classes that are in the modified file of course have to be rebuilt as well, since they still reference the old class.
All in all: highly recommended.