Well, there's various elements.
Personally, I find the beginning a little meh, as in the fights are damn fun but you don't really care much about the story itself, but once the main plotline strikes it gets miles better. The fights don't drop in quality or quantity, but now there's something to earn at every step.
And really, it's a place where you can really see Araki flex his creative muscle in terms of stands. It's like he ran out of the most typical ideas and, once forced to come up with something else, found treasure.
The characters themselves are great as well, you get to be invested in each and every one, and they all stand out well in one way or another. There's a lot of development in that aspect.
And finally, once you get past the fact Araki kinda forgot how to draw different faces, the art is amazing.
That's… basically my opinion there.