He started out quite badly, but by the time he was fired many of his players thought he had become a very good (or even great) coach. I recall reading several quotes from players who were very surprised that he was let go when he was, thinking that things were still coming together in a positive way. The defense still left a lot to be desired, but behind ****ey, Lofton, Jefferson, Coffman, etc. the offense was turning into an aerial circus that put a lot of points on the board. Obviously in retrospect they would've been a lot better off keeping Starr vs. hiring Gregg. Part of Starr's problems at the beginning (aside from his inexperience and coaching philosophy at the time) stemmed from Devine's infamous Hadl trade which robbed the Packers of important draft picks for a few years after.
