Love all the characters, the good and the bad. The relationships between them are a joy to see as they meet, grow, and interact with one another, whether for good for evil. I love the manga just for the characters.
I also love the story, a boy off to find his father... though I wouldn't want to find a parent who abandoned me to go have fun off on his own, but whatever, suits this story fine. I like the power growth, the training, and all the things the boys have to learn and how they go through each obstacle. It was a delight to see overcome trials without having to yell about nakama and such. The humor's pretty good too.
However, there came a point where I believe the mangaka got too much into strategy and away from plain old storytelling. He obviously is very good at stories, but something must have happened personally because HxH severely suffered at the Ant monster arc. Toward the latter half of that arc, there was much narration going on rather than dialogue, which resulting in him telling the story rather than showing it. That's like having more stage direction in a play than the character's dialogue. We want to see the characters act, not be told how they are acting.
It wasn't a bad storyline, it just dragged on for far too long, moving away from the main story, and if I weren't so devoted to the characters I would have dropped it. Two of the characters from the beginning didn't even make an appearance... for what, 150 chapters? 200? I've never been so relieved to start a new arc in my manga-reading life.
Once that long and tedious arc was over, however, the story picked back up to its original good pacing and plotting. The art picked up as well. Hopefully, if and when the mangaka starts this again, he will not fall back into a convoluted, unnecessary story and stick to the original heart of the manga.