I'm not a big fan of the series, but thought the finale was pretty good. Certainly better than some of the episodes.
Good Things
No "Anti-Super Power Ray"! No electric floor that can stun Superman without turning Batman into a burnt piece of bacon! When the Thanagarians went after the League, they did so with weapons designed for each of them. It's little things like this that make for a good episode.
Another plus, Batman wasn't SuperBatman.
And we got to see the team out of costume. It was getting silly seeing the members, unconscious and hooked to monitors in the headquarter's infirmary, still in uniform.
Speaking of being out of costume, we finally found out whether or not Hawkgirl's wings were real.
Lastly, the fact that the Thanagarians each had individual uniforms was a nice touch. Plus, I think Hawkgirl's uniform looked a bit like her "evil" version from the other dimension.
Bad Things
A Thanagarian invasion kind of screws with the possiblity of Hawkman joining the team.
The Thanagarians themselves honestly weren't that frightening. The ominous music followed by a pan up to reveal hawkpeople perched on buildings made me laugh. They looked like pigeons.
And did anyone else catch the swastika as part of the design to the Thanagarian machine? That's some subtle symbolism! It's almost like they're saying that the Thanagarians are evil or something...
J'onn: "I can't read the Thanagarians' minds." Flash: "Then how will we find out their evil plans?" J'onn: "I know, I'll read their minds!" Flash: "Um, I thought you said you couldn't do that?" J'onn: "Give me a break! This is a 3-parter, you know! I said that back in part one! You should get down on your knees and be thankful the writers didn't have me collapse, grabbing my head and screaming, for no apparent reason! Aw, screw it! I'm going to find Luthor's Anti-Superpower Gun. That thing will not only stop the aliens, but disable their weapons and ships, too!"