Plot: or a lack thereof.
Let me preface this by saying that I adore this anime. It's one of the most interesting, refreshing titles I've seen in recent memory. However, I feel like there's something holding it back from being truely excellent. As it stands now it's a pleasent watch but I can't quite bring myself to give it a perfect score - it's stuck at a 9/10.
I think the issue is the plot (or lack thereof).
Obviously the show is purely episodic, but I was watching it as it was aired (without any knowledge of the manga source material) and felt that there were a few opportunities for the show to really grasp onto a theme or plot element and pursue it in later episodes.
Some of the best opportunities might have been right in the first episode (The Green Seat) where the drinking ceremony was inexplicably interupted by a raven - since I was unaware of what the show was due to become, so I thought it might become a driving plot point. Or, much later in the series, episode 20 (The Sea of Brushes) when Ginko comes upon a mushi that must be trapped within scrolls or else an evil (of sorts) will be released upon the world. Since the series went on a hiatus at this point (we waited for several months before being able to see episodes 21-26) I thought that when it returned it would revisit that story for at least another episode or two. But alas, it was not meant to be. The series continued on as it always had.
I know it's redundant to hypothesize on what the anime could have been, since the series is complete. And perhaps I'm looking at it from to mainsteam a perspective - obviously the series didn't need a plot to be successful. Its lack of plot even went to shape the theme of the show that while we may be temporary, some things are eternal.
I just wish there were a bit more to it.