Do you have any info on it?
The FCS seems to be a juiced up, high tech version of the Stryker. Supposedly it will have better armor, but similar weaponry. The biggest change according to the thing I read was much more digital communications involved in it. The AGS version of the FCS looked much more streamlined and appeared to have a turret.
http://www.darpa.mil/tto/PROGRAMS/fcs.html
That's the link. Looks like it is supposed to work with the new Land Warrior system.