The main issue here is that if I'm editing tags in the main panel and I use CTRL+Z, it undoes the changes I made but it also deactivates the field I was typing in, so I have to activate it again before I can type something else. In the tag editor, it does as I would expect and undoes the typing while leaving the cursor in the field.
What I'd really like is for it to be context sensitive enough that I could configure it as the Undo Tag Changes hotkey in preferences, and still have it respond in text fields with the typing undo. I'm sure that's a taller order.