I generally make the map file as simple to read and change in a text editor as I can. This generally makes the python code to parse the file a bit more complex, but since this is done only once at start-up I don't notice any speed issues.
Another way of doing it is to write a simple map loader that then pickles the data structure and saves it, and then in your game, load the pickle file.
Pickling sounds awesome, looking at some tutorials on the web. It would be a good choice if the editor was made in python, and it could be pickled. Text just makes it simpler to start, but pickling would probably be faster in the end.
Thanks, -spot