I have been shooting semipro with my trusty steed...my D70 for several years. I feel I am ready for a real pro camera and I am looking at the D300. Because of expense ..I might have to go with the D200. I shoot mostly portraiture so the D70 has been fine for awhile. I have read enough to know that the change in cameras could be very jarring. What specifically am I going to find challenging in the new camera? Any advice?