I am seriously considering the possibility of using the 27in iMac as an external monitor with my MBP when I am home and need the extra monitor space. That would also allow my family to use the iMac when I am away at work or out of town. Since my MBP has a Mini DisplayPort, it should be as easy as connecting the MDP from the laptop to the MDP on the back of the iMac and then connecting the USB for audio? However if the iMac is turned on, how can I use the monitor without the actual computer running at the same time?