Story: Even though each episode is stand-alone, the amount of content and the depth in each episode could inspire a whole series. The whole series is very slow, but it does not drag; it takes its time, really allowing you to enjoy each scenario and contemplate the message.
Art: Beautiful background shots that look like they came out of a museum. The characters (besides the main) tend to look like each other, but that could be deliberate (people are more connected or alike than they think). The mushi all had clever designs, and were fun to watch.
Sound: A really lovely opening song. I didn't mind sitting through it (and I normally skip the openers). The background music was simple, but conveyed the feeling each episode was meant to. I watched the dub, and I think Travis Willingham was a great choice for Ginko; he has a soft, soothing voice that isn't flat or monotone.
Character: The main character, Ginko, was a great example of how a character can be subdued but not boring. His gentle actions really set the tone for the whole show. Every supporting character had distinct personalities, and made each episode lively.
Overall: A great show for relaxing. I loved the show for its gentle nature, and lovely art. Such a beautiful show should be enjoyed by everyone.
TL:DR 5 words/phrases to describe Mushishi:
beautiful, calm, supernatural, moral choices, relaxing
