Like you guys I thought it was Hershel's wife or other family up until the last moment, and the reveal made everything so worth it. Yes, waiting on them to find Sophia started to drag and was getting frustrating to the point of no longer caring, but when she walked out of the barn...what that meant for everyone...blew me away.
Now that she is pregnant, Laurie's worst fear is bringing a child into a world where it can't survive...and her worst fear was realized through Sophia.
Shane, who has criticized Rick's survival instinct all season, was not able to pull the trigger on her.
The two philosophies coming to a head: Are they people or are they monsters?
I've only read the first trade of The Walking Dead, which included the farm, and what the show did with the barn was far more powerful than what came through on the page...for me at least.
Yeah, I loved that episode.