> The final requirement for a reasonable IDE experience is to be able to follow a debugging session in the file where the code exists.

Having a cursor follow along in the file is just one part of a visual debugger. Seeing the call stack and being able to move up/down, the ability to see scope variables, the ability to enter console commands are all essential. Lack of these is why I stopped using SublimePdb, instead switching to pudb: https://pypi.python.org/pypi/pudb

I highly recommend it as the lightest weight interactive debugger out there for Python.