it's probably the best crossover DC's done in years so far.
Well, that's damning with faint praise. It's not hard to be better than Final Crisis or ICk or Shamazons.
To answer your question, it's just... uninspiring, IMO. Zombie Dibneys killing Kendra and Carter just as they finally accept their love, dangerously incompetent "look they may call themselves higher beings but they're actually lamer than us after all" Guardians, Pretty Princess Hal Jordan, savior of us all whom everybody loves and wants and who knows the secret IDs of everyone in the Batclan because why not, all-female Star Strippers Sapphires, offhand Laira fridging (what do you want to bet that's the one death that gets forgotten instead of reversed at the end of the plot), purely negative emotions (because as Bruce and Guy can tell you, anger has never made anybody do anything constructive or positive in the history of mankind)... Hell, the "emotional spectrum" in the first place, which was always a painfully stupid premise, and nothing like as elegant as "the first cops in the galaxy used green lights as a symbol." I was willing to run with it when I thought there'd be a good story coming out of it, but all that's happened is mediocre, by-the-numbers Event that hits on every cliche that's ever preyed on superhero comics, so there's nothing to excuse the weakness of the foundation for me. It's not awful or anything, I just can't find it remotely interesting, and it's annoying the way it keeps glancing awkwardly off or outright stalling out stuff I am interested in (J'onn, Babs, Bart).
I do like what Johns has done with Sinestro, though, the Soranik thing aside. So I suppose there's that.