I disagree. I find virtual desktops much easier to use than looking at a monitor that isn't in my field of vision. I would rather press a key than make my body uncomfortable.
(For this technique to work, though, you need to be very comfortable with the keyboard, and you obviously have to disable desktop-switch eye candy. Not a problem with xmonad ;)
I use virtual desktops and use multiple screens. I find it much easier to glance back and forth between two screens (or three, or four) than to switch virtual desktops and locate something. (This may be a training effect though)
(For this technique to work, though, you need to be very comfortable with the keyboard, and you obviously have to disable desktop-switch eye candy. Not a problem with xmonad ;)