I propose that when the 2.5 'space menu' first appears and there is no search text in the menu, that it shows an empty search box along with the old 2.49 style hierarchy menu. Typing into the search box would replace the hierarchy with the 2.5 style 'search results' scroller. Clearing the search box would again restore the hierarchy. The current functionality also brings up the menu with the last search filled in the 2nd time it's opened. This could be changed to show the last option used at the top of the hierarchy menu, but show an empty search box.
Here are some illustrations..This is the old 2.49 'space menu':

This is the 2.5 'space menu'. Below the empty search box is a scroller that seems to contain an un-organized list of almost every function in blender. In my opinion being able to scroll this top-level 'search results matching everything' is near useless...

I propose the 2.5 space menu look like this when no isearch text is entered into the box:

Then, when the user began typing, it would replace the 2.49 style hierarchial menu with the 2.5 style isearch results.
