Not me. To be honest with Rachel dead, Tobias undead, Marco sort of a sellout, and Ax the only real winner Jake and Cassie's problems didn't seem like problems, they seemed realistic, there was no happy ending to Animorphs, it was sort of like in the field of happy endings they won most of the battles and then lost the war. We got sappy ending after sappy ending, with close call after close call the fact is K.A. warned us what would happen but she never really prepared us for it, we were shell shocked and it was brilliant.
Irritating in some ways, but brilliant. It made the ending harder to forget, maybe some people were more willing to foget it but for me at least it wasn't possible, if Cassie and Jake ended up together all happily ever after it'd be like any other story, in the end the hero gets the girl, rides off into the sunset the badguys thuroghly beaten down.
Besides, as Nohensen points out she kind of walked out on him when he needed her most, that's pretty low in my opinion, if she wasn't there for him then how could they have made a life together? He pretty much lost interest in her too, he was too torn up with his own grief and I don't think he ever fully trusted her after she let Tom go.