Spoiler Level: High
A nice follow-up to "Luthor," and I like the parallels with the title names. I'm not quite sure all of the logic regarding the mirror box was consistent with how it was portrayed in "Luthor," but if you don't think about that part too closely it's an enjoyable episode.
I guess I assumed that the series would have Martha Kent coming back to the farm, since the Superman mythos usually has Clark in Metropolis with his mom on the farm. But that doesn't really work with Martha being a senator now, so this way works well for the show. The thought of the farm not being in the Kent family at all actually makes me a little sad, but hey, at least they didn't blow it up.
The idea that Clark Luthor is only evil because he was raised by Lionel Luthor instead of Jonathan Kent and Jor-El certainly makes this a different take on Ultraman-- I don't recall Jor-El being addressed in any of the Crime Syndicate stories I've read, but I'll bet in his universe he sent Kal-El to Earth to conquer it. That's obviously not intended to be the case here, as we're left with the hope that Jor-El will put Clark Luthor on the straight and narrow.
I also really like how Clark Kent is becoming the kind of character that inspires people to be better, such as he did with Earth-2 Jonathan and, eventually, Clark Luthor. That's the kind of character that Superman is meant to be.
And damn, Tess's dress was distracting.
Thanks, as always, to Home of the Nutty for the screen captures. And as always, as of this writing, this episode is available to watch online (with commercials) for free at http://www.cwtv.com/cw-video/smallville/.