Knightmares was the BEST and was exactly as long as it should be. Only real problem was the first issue was pretty bad, and the Flash crossover in the middle was terribly timed and not very good.
As for the current Batman run, my biggest worry is that it's going to be a shallow "deconstruction" of Batman like Si Spurrier's Worlds Without A Justice League: Batman, only longer. But I have more trust in Zdarsky than Spurrier, so I think it'll probably be better.