i dont know why people are complaining about the slow development, you need to understand that this manga is a parody and is mainly for comedy, it isn't meant to have a proper storyline and have all the interesting arcs come one after another, it is usually 3-4 small arcs and then one big arc
and yea hayate has a bit of a harem but its not like all the girls love him and who says this new girl is gonna end up falling in love with him.