This has been an annoyance for a while now. On my laptop, where the screen isn't huge, the headers display area is way too large, and is mostly whitespace and redundant info I could see from the message list. It literally takes up a fourth or third of my reading pane area, depending on if I scrunch up the message list - but I want to see the message list.
There has got to be a way to either hide this header info, or compress it so that so much screen space is not taken up by it.
Here's a screenshot illustrating this. I know others have complained about this as well but I want add one more mention. After all, they say for each person you hear from, there are 100 more with the same complaint that don't bother.