The Awesome window manager has me slightly impressed.. who knows whether I will continue to be impressed in a few days, but for now, I am. I found myself somewhat frustrated with the standard GNOME desktop when using multiple monitors in a Xinerama layout (the default if you just plug a screen in). Awesome is a tiling window manager.. in the past, I haven't been inclined to use one, because I work mostly on a single screen, or I have enough screen space for all my current work to be focused. My current work environment, however, involves a bit of task switching, and having a big monitor on my desk as well as the small laptop screen means I want better control of my windows.
The key feature for me is the ability to have independent virtual screens on each monitor, despite it being Xinerama. Most of the time I want the Windows VM showing on the laptop screen, but not always. In my current work environment, having tiling windows is actually proving quite nice, and it's helping me to be a little more organised. I split my tasks between virtual screens, and keep an eye on the Windows VM & outlook on the laptop, so context switching is easy.
Of course, some windows should be floating, and Awesome supports that just fine, as well as allowing each virtual screen to have its own layout style, and easily switch between them.