I used to have four monitors on my work computer, but once I got it into my head that I could have eight, I was simply unsatisfied with just four. Yes, I use them all, every day.
The upper left screen has my email (Thunderbird). To the right is my database client (SQuirrel SQL) but also the console screen for my Java GUI (Eclipse). To the right of that is the Eclipse editor. On the far right top is the Eclipse project list, Eclipse server list, and the Eclipse process list. The lower right screen is my browser (Firefox) and often I open Firefox in the screen to the left of that. The two middle bottom screens both have a text editor (Emacs). The lower left screen has an ssh connection to one of the many Linux servers I work with. I often open a second ssh window in the screen to the right of that one.
So, despite having eight screens, I still jump between different windows on many of them. In other words, if I had four more screens, I’d use them. I use two Vidia Quadro NVS 420 video cards, configured in X Window very carefully. Sadly, the computer that my workplace has provided only has slots for two cards.
You’ll notice my cool contoured keyboard, and I have a spare “guest keyboard” for visitors who need to type something and are intimidated by the keyboard.