We probably need to see some example picture with the EXIF data still intact for a good diagnosis.
As the resolution of the sensors get bigger, they will more quickly show problems with your hand-holding techniques. Slightly faster shutter speeds can help. While the old guideline of "min shutter speed = lens focal length", it seems to have moved up to 2x the focal length these days.
Check your picture control settings for sharpening. By default they are set pretty low. On your D300 you may have increased it to suit your tastes.
---------+---------+---------+---------+ Joseph K Seattle, WA, USA