The Omnibus Collector talks a about that for some of them in his review of DC's spring catalogue. Just go to theomnibuscollector.com and it should be on the front page.
The big question is what happens when the creator's most associated with a series leaves. I don't think they have come that far on any of these yet, but Nightwing should come to the end of Chuck Dixon's run with volume 7. It will be very interesting to see if they continue the series with the "lesser" creators in place. I certainly hope so as I'm loving these releases.