In the example above I edited KeyboardShortcuts.txt and changed the shortcut for delete to just E. Because the first short cut (alpha-numerically) is the default that spacebar will fire, E will now delete selected elements when I hit spacebar. Save this text file and restart Revit to load the changes.
Now go crazy. I bet there are a lot of old AutoCAD commands that will make sense in Revit. It helps when you switch between the programs, and it makes some people more comfortable and fast.
It's a good thing.