I find that universal shortcuts in Windows programs are a way to make the user's life easier. For example, you know that Ctrl+O opens a document, Ctrl+S saves it, etc. Similarly, you know that Ctrl+W closes the active document. Well, it does not with Trados TagEditor. What it does is to toggle show/hide hidden characters (the same thing can be achieved in Word with Ctrl+Shift+8).
I find this most unnerving, as well as the fact (?) that there is no close document shortcut in Trados TagEditor.