I have mixed feelings on the cliffhanger ending. On one hand, I was really getting into that sub-story, and wanted to know a lot more, and was frustrated when it ended so abruptly. On the other hand, it was definitely unexpected, and kind of made me hope that a sequel might occur at some stage.
I think I kind of am starting to understand why people were so anti the ending, and why I don't have a problem with it. I think a lot of people really cared about the characters, while I personally didn't really. I think the characters were pretty cool, but not enough for me to really love them and root for them and their relationships. I guess I was always just more interested in the plot, and I guess that's why I wasn't so annoyed Rachel died and that Cassie and Jake never worked out. It probably just didn't mean enough to me.