I don't feel at liberty to discuss his personality (as many online commenters are wont to do) since I've only met him once and it was for a tournament set.
From a spectator standpoint, I kind of like his position as "the guy to beat" since every win over him feels triumphant in a way that not many other players create. He kind of fills the void armada left pretty well in that sense, with more of a "villain" edge rather than an awed admiration.
As a player, he's obviously very skilled and there's probably a lot to be learned from his playstyle for people of any main. I still believe puff is a relatively bad character compared to most of the other top tiers, Hbox just happens to be extremely good (once again, similar to Armada with peach)
That being said, I almost never root for him, but who enjoys rooting for the best player anyway?