I find the way OS X handles windows is so much better suited to multitasking than windows.
In windows I'll have a single window taking up the whole screen whereas in OS X I'll be running 2 or three apps all on the screen, with the web browser that would usually be full screen taking up about 3/5ths of the space with Adium and Colloque sitting next to it.
I wish I could use it all the time.