I like information associated with my incoming emails. It alerts me to the fact if an email may be a new suspicious member, or if I should give the email extra attention. However, I have no need to see the header information all the time. This is especially true when accessing my email on a laptop. With full header information, my reading becomes "keyholed" into a tiny slot at the bottom of the screen.
Sure, I could switch my layout, but I don't like the vertical look on a tiny laptop screen which squashes everything into an unrecognizable mess. It's my computer and I have my configuration the way I want it. Thank goodness for this add-on. I can now read my emails without slouching, squinting, and turning my head nearly sideways for this basic task.
This review is for a previous version of the add-on (2.1.0).