Not to state the obvious, but spoilers. It's an old game, but I just go through it and 400 Days that I got on sale.
When Lilly straight-up murdered Carley, I wanted to restart the whole episode right then and there. She was obviously being set up as a love interest, but I wished there was something I could have done (from what I understand, no I couldn't). Fast forward to 400 Days, Russell jumps down next to a corpse and when the camera angle changes, I recognize the purple coat and feel it all over again. God damn it.
That's my story. I still didn't redo the episode - I figure this game is all about consequence, and any deviation from the "one truth" of the playthrough would be a betrayal.
What about you? What are your regrets? Did anyone actually replay a section? If so, how could you?
PS For those who did leave Lilly, is she there with Carley/Doug, or not?