How many neat bows do you like to wrap up your story threads?
I have two takes on this. No one, including myself, likes to see an important plot point, particularly an interesting one, die halfway through the story with questions left unanswered. Even minor characters and plot elements need some sort of resolution so it doesn't look like the author just forgot about them.
But if things are too neat, if the story is tied up so completely that there's no wiggle room for what happens next, then my imagination goes to sleep. I don't always want to know exactly what's going to happen next. I want to imagine it for myself. This is why I wish The Matrix saga had ended after the first movie - humans hadn't won yet but they now had the means to win. The filmmakers pointed the way and it was fun to think about how our hero might achieve success.
At the end of Song of Scarabaeus, there are a couple of plot elements left hanging. One is rather important (a character is dying) and arguably demands a sequel - the "cliffhanger". But in this case, the characters discuss exactly what they're going to do to resolve the cliffhanger. If there were no sequel, the reader could assume they did just that, and succeeded. In other words, I pointed the way. I don't really see it as a typical cliffhanger.
The second unresolved plot point isn't a cliffhanger but it follows that same idea. Our heroes have obtained the means to help lots of people. They discuss exactly how they're going to proceed, so the reader can assume that's what they do. (Of course, in reading the sequel you'll discover things don't go according to plan.)
There are other plot elements that could be considered unresolved, I suppose: Will our heroes evade the Crib? Will the leash be cut? Will Finn and Edie get it on? Well, I had to leave something for the sequel! And the story works without precise descriptions of "what happens next." If there were no sequel, I love the idea of leaving the reader to imagine what happens next.