Maybe some of you like the idea and are willing to implement it... I might write out some pseudo-code that could be converted into real code if I get around to it.
I think pressing the spacebar should only show the options that are valid at that time. Also, it should show every valid option.
I think that initially, the "Edit" category should have hardly any entries... just things like
Grab/Move G (I think including the word "move" makes it easier for beginners to understand - they might ignore that entry if it just says "Grabber")
Type in Position/Rotation/Scale N
Enter Vertex Edit mode TAB
At the moment it only has one entry for "N" - it is under sequence - it is for "Str Params". But usually selecting that on the menu does nothing - since I wasn't in the sequence editor (or whatever).
So basically at the moment, you can get an incomplete list of hotkeys, and many of them don't even work when you click on the menu. Sometimes using the menu does work, but the hotkey is misleading...
e.g. if you aren't in edit mode and you go to shear (Ctrl-S) it works - because it takes you to edit mode first... but if you aren't in edit mode and want to use the hotkey, a beginner would assume that Ctrl-S is all that is needed... but Ctrl-S makes the Save file thing come up! (Ctrl-W is meant to be for that...)
And sometimes the menu doesn't take you to edit mode...
e.g. if you go to the edit menu and go to shrink/fatten (alt-s) it says "clear size?" !
I think the descriptions should be more descriptive....
"Join" could be "Join selected objects"
"Make Track" could be "Make 1st selected obj track 2nd obj"
"Make Parent" could be "Make 2nd selected obj parent of 1st obj"
I think there should also be some information included with blender that explains everything you can do with the mouse (move things, create new views, etc) and that you can press space to see the other relevant commands. Maybe the mouse stuff could somehow be on the spacebar menu - it could have a link to message explaining about the mouse.
I guess "enter vertex editing mode" or "edit vertexes" (TAB) should only show on the menu when an appropriate object is shown - e.g. not a light. And if a light is selected, things like the light properties (F4) would appear on the menu.
Maybe the first time blender is run it could have a little message that talks about the mouse and the spacebar menu.