I think switchable is something different; ironhide/bumblebee are for the newish "optimus" setups, which currently only work properly for windows AFAIK. It's quite neat: rather than switching between cards, the discrete card is used only for the windows/apps that need it, while the integrated card handles the rest of the desktop.
The ironhide/bumblebee solutions work by running another X display, and using virtualgl to draw the window from the discrete card on the main desktop -- but you have to explicitly invoke the applications that you want to run in this fashion.
The ironhide/bumblebee solutions work by running another X display, and using virtualgl to draw the window from the discrete card on the main desktop -- but you have to explicitly invoke the applications that you want to run in this fashion.