I jumped from the FD70 to a FD135 so I may not get some of the changes from the FD75 to the FD1s correct.  Auto lateral tilt, extra reel fingers,etc. have been mentioned, but two of the changes I like on the FD1s are that the head runs lighter on the ground and I especially like the matched feeding of the center belt and drum to be brand and model specific to the combine.  I always thought the MacDon heads were better matched to JD combines than CaseIH.  The feeding is definitely better for CIH machines with the changes.  In cab draper speed control is nice when you need it.

Chain tension adjustment is much improved for the center drum and they are supposed to have fixed the chronic oil leak issues with the pto driven gear box.  The seals used to be attached to the bearings and didn't last after some age on the header even after rebuild.  Potentiometer cables have been changed to prevent premature wear from rubbing.