Plot: Takaya does occasionally lose focus and tell us everyone and their grandmother's backstory, and it sometimes seems like she's forgotten who the three main characters are supposed to be. Also, BE WARNED. Around the introduction of Rin (volume 9 or so), the series starts to take a really dark turn. If you've only watched the anime, this could be a real slap in the face.
Length: This series is pretty long for a shoujo, at 23 volumes, and sometimes it seems to drag (especially at times when it's focused on a character you may dislike). It takes commitment.
Characters: This is far and away the greatest thing this manga has to offer. Takaya did a brilliant job in this department. There's bound to be at least one character you like. And although you may not like where they end up, all of the characters undergo some sort of change during the story. The side characters are excellent. My main problem was with the main character. She annoyed me for most of the series. However, the whole stepford smiler part of her nature was a pleasant twist, and her cheeriness in the earlier part of the series took on a whole different light. The characters are where Takaya excels.
Art: The art is pretty typical shoujo. You have a bunch of bishonens, but nothing that really stands out.
Possibly Offensive: Most of the time I'd discuss violence or fanservice in this category, but Fruits Basket offers something else entirely. Where this manga excels is in playing with your mind and your heart. It can at times be psychologically disturbing, as it touches on some pretty deep subjects such as abuse, neglect, and parental abandonment. It's not some light-hearted shoujo for little kids.
Other Comments: This was my first manga series, and a lot of other people's as well, it seems. This was also the series I used to get my sister to read manga, and now she has become addicted to many other series as well, like me. This is certainly not the greatest manga out there. However, it is good for getting people into the world of manga.