The premise is unusual, so there are a lot more opportunities for humour than the typical "house-sharing with strangers" setup allows. And unlike the anime, which -- while nice enough considering its indubitably tiny budget -- skipped over a lot of establishing character moments, the manga takes it slow, so the gags are that much funnier (and the touching moments that much sweeter).
The characters aren't overdone stereotypes, which is quite a rarity in the gag genre. They don't behave that abnormally, but the sum total of their individual personality quirks never fails to transform everyday occurrences into silly shenanigans. The art is nice, too; pretty enough to earn the 'shoujo' tag, but goofy enough to suit a comedy manga.
The first volume is a bit awkward in of pacing and some of the jokes fall flat as the mangaka sets up the premise and introduces the majority of the cast, but after that the humorous aspect improves rapidly and the flow of the story becomes much smoother.
As for the "sexual allusions" the previous commenters are so hung up on: they involve the protagonist's brocon younger sister, feature in maybe three pages per volume, and are entirely ignorable. If you read shounen or seinen at all, you'll never even notice. I don't approve of it, obviously, but it's not a deal breaker by any stretch of the imagination.