I undersand that the HD-SDI out the EX cameras offer full resolution monitoring, and also a raw 4:2:2 feed from the camera head for those more demanding situations.
Is it possible to connect a SDI output of the EX1 to a firewire 800 inputs in the MacPro to give a better quality clip to be saved on the hard drive than using a simple USB output of the EX1 to a USB of the computer?

here ya go....

AJA Video - Serial Digital Video Interface and Conversion (http://www.aja.com/html/products_Io.html)

Two very different protocols, so you will need a converter to do this. Check out Blackmagic Design or AJA or Convergent Design. They are not cheap.