If single selection (by spacebar) then pressing spacebar and pressing Enter should typically have same action. i.e. select current row and fire_event.(X)
If multiple selection, then Enter typically fires an action for current row such as opening an item or giving more details for that item. Spacebar selects multiple items (or Ctrl-Spacebar), and other keys will execute some action on selected rows (like delete, flag, move etc).
(X) Exceptions: in tree, Enter collapses or expands, and selects current row, whereas spacebar only selects and displays in other window. Spacebar does not expand or collapse tree node. Typically in multiple select, spacebar selects first row (deselecting others) and Ctrl-Spacebar continues selection. Have to check this out with Listbox. including ListSelectable should take care of most of this.
