I see all these streamers (e.g. EGIdrA, FXOShelth, etc) switching out of SC2 and onto their music player or justin.tv channel with little to no delay. When using alt+tab there's quite a few delayed seconds before I'm able to interact with the new focus in any way. Is it some windows 7 shortcut, or some fancy keyboard with a binded button to desktop?
They are playing Starcraft 2 in full screen windowed mode. This allows for much quicker swapping, but only if your system can handle it. Full screen windowed mode is a little more system intensive than just full screen mode.