I think this may be one of my favorite episodes of the series. As much as I love Lois/Clark, on Smallville I've always been happiest from a storytelling point of view when they focus on Clark and Lex. The premise fo this show was always rooted in the different paths Clark and Lex were taking, and nothing highlights that more than parallels and contrasts between the characters.
I was a little disappointed that lionel was a physically abusive father. I always saw him as abusive with words and with his mental games, but not one that resorted to physical violence. But I suppose it makes sense. This helped remind us he's not a great guy.
What made more of an impact, though, was Lillian. Lex keeps Lillian on this pedestal. But the series has done a great job of hinting at the type of person she was, even while still allowing Lex to hold a torch for her. She was the one that killed Julian if I recall? And here, we see that she can be just as cold and manipulative as Lionel.
Clark was truly heroic in this episode. Kara and Lois were great. Chloe and the conflict over her powers was fabulous. Lex was amazing.
And we finally see why Clark will keep trying to protect and save Lex years from now. He's always going to hold onto that hope that the good part of Lex - little Alexander - will one day win out. Alexander loves Clark and considers him his best friend. Clark will never turn his back on him.
It doesn't get any closer to Superman than that :)