i only pre-wash fabric that will be used in a quilt that is meant to be used and washed repeatedly.
if its a wall hanging or art quilt i won't pre-wash but i do steam press the fabric when i iron it.
if the fabric has gold paint on it (mainly asian/japanese quilt fabric) i won't wash it because i've had it turn green and in some cases wash completely away.
i only use spray starch for more structured projects like handbags and clothing.