For its manga artstyle, you maybe slightly dissappointed (and maybe a little bit annoyed) for its rough-ness. But I assure you, its storyline, character development, all is in perfect order. It has harem style inserted, with Hayate being loved by almost everyone around him, makes you kinda eagerly awaiting who he end-up with. It also has tsundere characters, too shy to confront their feelings to Hayate. Additionally, it also has reverse love (SPOILERS: Kotetsu fell in love with Hayate-kun, and Miki Hanabishi, who secretly admired Hinagiku).
But most important of all (to me, at least), this is one of the manga that makes me cry (it is a manly tears, even if its a little). I literally cried during A-tan's arc (later part of Volume 17 and earlier part of Volume 18, chapter 178 to 187 to be precise), although it depicts on Hayate's childhood memory, it really gives an impact, and makes me cried the whole chapter when I'm reading.
That's all for now. Do read the manga as I managed to read all 413 (at this time) chapters in only one whole day and one sleepless night. Maybe you can call me obsessed too, since I've watched all season of its anime version and OVA. Adieu!