I prefer it because I read by scrolling down one line at a time. This means that when I want to go back and read the previous couple of lines, I have to scroll

I prefer it because I read by scrolling down one line at a time. This means that when I want to go back and read the previous couple of lines, I have to scroll up. This shows a big stupid menu of unknown size and behaviour on top of the text I'm trying to re-read. The biggest problem for me is the randomness between different sites. It's not a problem for Firefox to display a header when I scroll up, since I can predict its behaviour. My muscle memory adapts by scrolling up and then down again without conscious thought. It's a much bigger problem if every site shows its header slightly differently. I think the key thing is that when I scroll up, 95% of the time I want to see the text up the page, and at most maaaaaaaybe 5% of the time I want to open the menu. This is especially true if I got to your website via a search engine. I don't give a damn what's hidden in your menu bar unless it's the checkout button for my shopping cart, and even then I'd prefer you use a footer for that.