Something some of you seem to forget is one of the most importent things, motivation. It was clear already after the loss against Liverpool, which Given branded the lowest point in his career, that he didn't had the motivation anymore to fight day in and out with a team that only went downhill. Also when he joined City he said that he was really looking forward to the training on monday, like he had not done that for awhile in Newcastle.
Based on this I think he left in just the right time. I rather have an eager Harper that now has the chance to show he can fill the void from Given, then having an unmotivated goalkeeper, that just wished he played in a better team.