I actually liked this a lot. It wasn't as much of a nonstop action show as I'd heard; there were a lot of good moments of characterization and humor, and a lot of it worked very well. These are effective and likeable versions of the characters, in many cases. Wonder Woman is fun, and the interplay between Batman and Carl Reiner's Wizard Shazam was terrific. Some of the voices will take some getting used to, though; it's weird to have a Plastic Man who isn't Tom Kenny and a Constantine who isn't Matt Ryan (plus, why is Constantine even in a kids' show?), and it's awkward to have Billy Batson played by Sean Astin pitching his voice high instead of either an actual boy or a woman (e.g. Tara Strong, who's done Billy before).
There were some very clever moments in the action, too -- I was grinning when I realized why they'd had Calythos absorb Martian Manhunter's powers.
Still, there were some plot glitches resulting from doing a single story across four segments apparently written by different people. Like, first Jimmy Olsen had the insight that Calythos was absorbing people's powers because he'd possessed/merged with the Parasite, but then in the next segment everyone was assuming the power draining was Calythos's own ability. And there were only five demons to deal with even though Black Adam sent dozens through before those five. And the Wizard said he'd sent Black Adam to the far side of the galaxy, but in the final segment it was changed to the distant past. I'm surprised nobody caught those discrepancies.