i've found that it's not that i don't like Cassie, but i just LOVE the other five and was always more indifferent to her.
plus to me, her books were the most boring. i mean, granted she had her hugely important ones, like 4 and 50 and the ones with Aftran, but she also had the horse book, the amazing morphing-buffalo, the Australia one and a bunch of other fillers i can't even remember the plot of. while some of her moralizing annoyed me, if i had to say why i don't like Cassie, it was just because i didn't like her books.