I recently came by this useful tip on Lifehacker, which explains a taskbar trick that can save you some effort. If you have multiple windows open, you can CTRL + right click on them to select all of them. You can then right-click on one, and choose from the regular window options such as close, tile, or cascade. Good for closing a bunch of errors, or pop-ups at a time. (Not that I receive any pop-ups using Firefox).

Being a student, one use that instantly comes to mind is for copying data between windows. If you are writing an email or trying to copy something down from another source, it can be annoying to switch back and forth from the task bar. Much easier to tile both windows vertically, so you can view both items without hassle.