So I currently have a dual-ati video card setup on my laptop. A low-power one and a high power one.
In windows 7 the drivers switch video cards when on external vs internal power. Also one of the video cards contains an HDMI output which I would like to use as it lets me plug in my monitor.
So ...
Hybrid graphics has improved a bit lately. The latest Catalyst drivers provide a login/logout switch. Have a look at these websites:
https://launchpad.net/~hybrid-graphics-linux
http://linux-hybrid-graphics.blogspot.com