Mushishi has always had a special place in my heart.
I will make this clear right away: if you are looking for intense action, an epic overarching plot, or flashy animation, this isn't the right anime for you.
No, what Mushishi does best is make you think. It explores interesting situations, without beating you over the head with philosophy. No ideas or specific dogmas are forced upon you.
Nature plays a large part in this anime. Much of the series takes place in the wilderness, or at least in isolated villages. Scenes of nature are rich and beautiful, showing great attention to detail. I also found some of the 'mushi' designs to be rather interesting. The little creatures come in all shapes and sizes.
That said, character designs are poor. Many of the supporting characters look like they are recycled from episode to episode. Ginko and a few select characters are unique, but most are indistinguishable.
The episodic nature of Mushishi lends itself well to the series. Each episode is completely self-contained, telling a story unto itself. The creators do a good job of bringing each story to a satisfying conclusion. Even though the minor characters' appearances are resused, their personalities are not. Many intriguing souls pop up through the series' duration.
The music is fairly peaceful, as one would expect. It does not call attention to itself, nor does it detract from the story.
Do I recommend this anime? Yes. If you're willing to take a break from ninja fights, mechs with beam weapons, and ridiculous ecchi shots, this show could be for you. Just be patient, and think a little about what you're seeing.