I upgraded to Firefox 3.6 just to try it out. In Windows 7, it did this subtle thing which completely annoys me and forced me to uninstall.
In earlier versions, the window at the bottom worked properly. Now, it creates this multiple window model in the bar. When I CLICK on the Firefox icon, I get the following:
Now, I used to get something VERY different. I used to get the browser popped up. They did something where the tabs = windows. I want the tabs = tabs! Now I have to click, sigh annoyingly, roll my eyes, move the mouse up, randonly pick a tab, then click again, then wait, then blog about it.
Little things that are annoying, especially in highly used software, creates cumulative stress and subsequent user failure. This is one such example. I might downgrade.