well I guess this series is one of those examples of "it's not the destination that matters, it's the journey" where the ending is meh but the series itself was really good. Although come to think of it there wasn't really any closure on anything at the end (aside from some relationship mending). but none of the romantic relationships were ever solidified, and we're not any closer to finding out what heartseed was or why he was doing all of this (unless it really was just for his own amusement). It seemed like he was trying to make them learn more about themselves but then, again, why would he do that in the first place?
I am so bad at predicting twists. The only one I could guess is that the issues they were having during the "unleashed desires" sequence would be solved by turning the problem (of getting emotionally involved and hurting others in the process) into its own solution. That was a good closure. I'm not really sure if I liked how Nagase's identity issue was solved though. There's always something awkward about those epic self-reconciliatory moments in anime.