I forgot to mention that this handles dual monitors without issue, and goes from docked w/two monitors to undocked with one monitor seamlessly. If you decide to exit it, all applications collapse to your single desktop.
The one issue I have noticed is that if you have an open dialogue box it will likely die on desktop switching. This is a minor annoyance, but not one that has caused me much heartburn (and believe me, I have lots open, two and three copies of visual studio, and similar instances of SSMS running at a given time).
Sorry, should have thought all that through in my first post.
I too am using mDesktop. It has proven easy to use and configure. I particularly like that I can set windows with certain title text as visible in all desktops, so Trillian is always around but my various tasks can be separated. I recommend it and have gotten a bunch of guys at the office using it too.
"'Tis true, 'tis pity, and pity 'tis 'tis true." -- Poloniouius, in Willie the Shake's _Hamlet, Prince of Darkness_