Actually he uses it, I imagine, so that he will be able to read it next year.
I haven't even tried to use any todo apps, (the text file has always served me well) but what experience I have with proprietary formats is that they're a poor choice for storing data, since either they're poorly designed or the designer is constantly redesigning them and invalidating your data.
That's why the statement was doubly odd, because todos are pretty transient.
I like Things for Mac myself because it automates repeating and scheduled todo items, and has a distinction between completable projects and areas of upkeep. A programmer can leave any time they want by processing its XML file.
I haven't even tried to use any todo apps, (the text file has always served me well) but what experience I have with proprietary formats is that they're a poor choice for storing data, since either they're poorly designed or the designer is constantly redesigning them and invalidating your data.