With a large, wide monitor, I run very few things maximized other that a browser and full screen games.  A much smaller notebook screen would be very different.  For Idle, I want Shell and Editor side-by-side.  I would however, like windows vertically maximized, as with Window => Zoomheight, except that Zoomheight is buggy in that it ignores the taskbar and puts the Idle status bar underneath.  (Maximize does not do this.)

The idea of removing the option and remembering the last position is worth considering, but there may be multiple windows upon closing.  I would actually like the horizontal positioning of shell and editor kept separate.  So I agree that initial window size and position could be improved, but I am not sure how.