It's a tough nut to crack, but great software to use for interactive stuff. If you're into video installations you should check:
www.brendandawes.com
He's an expert in MAX/MSP and he has ready to use patches/modules.
I downloaded the video delay patch and connected my video camera to my mac.
Delayed footage 4x4 screens realtime!
Just click on the downloads button on the left side of the homepage for more goodies.
Have fun.