Unfortunately, the main motivating force of this story seems a little week - Lex Luthor comes across less as the desperate opponent of "Injustice for All" and more as the generic bad guy with a power suit that needs repairs and can blackmail someone (Mercy) into helping him. Sure, there's a scene or two of Lex grabbing his chest and moaning in pain, but overall the whole thing is rather...relaxed. There's no real emphasis on Lex dying here.
(One also wonders why Lex is just flying around Metropolis blasting the heroes, but anyhoo...)
It is nice to get an update on LexCorp these days, but Mercy (previously a hard-boiled martial artist/bodyguard) gets a new hairdo and seems like an entirely different character. The hints of a relationship between her and Lex are kinda interesting for a "kids" show and are done just right.
That brings us to the real antagonist - "Amazo." Although never identified by name (a cute touch), we'll keep referring to him as such (as the credits do). We don't see much of him here personality-wise, and Robert Picardo is barely recognizable as the voice-artist. Amazo's powers (which seem patterned more on Marvel's Super-Adaptoid, then the comic book version of Amazo - Amazo never gets wings and weaponry, for instance) seem really, really, powerful. So he can see someone and adapt their tactics as well as their powers? Presumably there's a lot more going on then just visual scanning, but still I'm not sure I buy him creating a duplicate power ring. He does make a suitable menace against the League, although I wouldn't have minded GL, Flash, HG, and WW make a little better standing against him. Their lack of teamwork seems pretty obvious here (although that may be addressed down the road in "The Secret Society.")
The animosity between Superman and Batman (from "Twilight") seems lost here - from what happened in that episode it's hard to imagine them casually hanging out in the Batmobile (although the bit of Superman drinking coffee is cute). This is really a Batman/Superman-specific episode - they're the ones who outthink Amazo (even if Superman's blindfold ploy ultimately fails) while the others kind of sit on the sidelines.
Except for J'onn, which brings us to the B story. The storyline subtly emphasizes one thing, which is that J'onn doesn't seem to have much contact with humanity other then his teamates or the bad guys they fight. With the exception of GL (in "In Darkest Night" and "Metamorphosis") the League members don't seem to interact with normal humans except to rescue them. J'onn continues to be the "heart" of the show, providing some much-needed emotional content.
One last thing is that Superman tends to dominate a bit here - Superman leads the fight, Superman is most effective against Amazo, we have a major Superman villain as the protagonist. Hopefully they'll vary this a bit but having "Twilight" and "Tabula Rasa" in sequence, both being Superman-centric, might not have been a good idea.
Overall, this episode does a decent job of setting up part 2 and the final battle.