Just finished this a couple of days ago. I enjoyed it, though not as much as the earlier installments. I agree with what has been said here so far about the Nimbus III and Defiant plotlines - although it was interesting to see how the Planet of Galactic Peace began and ended in flames, it could have tightened up the story to jettison them.
However, I disagree about the treatment of Quinn. I think they're setting him up for a rebound in the next book, giving him a character arc that makes sense from the personality and character that we know. I look forward to seeing what they do with him in the next book.
Argh, March 2012?!!! Hurry up!