Yeah, watch it.
Its pretty slow paced and mellow, but the artwork is really nice and its all very relaxing to follow.
A note, however: I'm not sure if you can truly marathon Mushi-shi. Each episode is a story within itself, very rarely is there a correlation between stories. There are references here and there, but for the most part they are all self contained. For this reason, there is no "cliffhanger" drive to watch the next episode and it might be hard to spam through it.
Instead, I very much enjoyed using it as filler between regular releases. Watched one or two episodes every few days and it was fantastic like that. Because each story is unique and different, its like watching a small movie every time.
So yeah, watch it. 9/10. "A must see". "5 stars".