First and foremost, I think Takehiko Inoue is fantastic. I started reading his stuff through Slam Dunk, then migrated to Vagabond ~2000, but it was truly through the Viz releases that I started really appreciating it.
I like Vagabond for its characters primarily. I like how he portrays Musashi not as the perfect sword god that he's been memorialized as, but a talented, troubled youth who regularly takes one step forward and two steps back along the path of enlightenment. The more you dig in, the more there is to see. That being said, I maintain that the series has been in a rut for several years now as Inoue very clearly is struggling with how to wrap things up (he's been trying to for years), and it just doesn't quite have the spark it once did for me. Still, that certainly doesn't diminish what's great about it.
If you haven't already, I'd highly recommend looking into the background of the real Musashi's life and at the least, familiarizing yourself with the novel that it's (at least nominally!) based on. I think that context isn't spoiler territory, but rather it adds meaning to the choices Inoue made in how he portrays the characters in his version of the story -- Musashi and Kojiro in particular are dramatically different from the novel.