SPOILERS (left click and drag below to read):
They did it. The one thing I was hoping they wouldn't do. They killed off Shane. My favorite character on the show, because he was the most flawed and conflicted. I knew he died early on in the original comics, but appreciated how the show's makers were kind of doing their own thing, separate from the comics. In the comics, Shane is killed by Carl when Shane tries to kill Rick. Carl shoots him through the neck. And they did pay homage to that in the show, with Carl killing zombie-Shane.
But the fact remains that a huge part of the drama on the show is now gone. I've long said the show needs the kind of conflict like that between Rick and Shane to keep the more dramatic elements of the show to continue, and now I'm wondering where they're going to go from here. From a writer's standpoint I think they shouldn't just consider Shane's death the end of that particular story arch; I think starting with the new season we need to see the long term affects of Rick's hand in the killing of a man who, while he may have been jealous and covetous of Rick's wife, was nevertheless Rick's partner, right-hand man and best friend. Just because Shane is dead shouldn't mean his story is over.
That said, I'm anxious to see what happens next week. Obviously, as the teaser showed, a horde descends upon the farm so it's going to be time to pack it up and move on to a new location. And I'm sure we'll probably lose a couple more major characters (I'm guessing T-Dog and Carol, or maybe Hershell and his family).
Regardless of what happens, I'm in it for the long haul with this show. While they've done things and killed off characters I prefer they wouldn't, they've yet to make anything like that feel forced or tacked on just for shock value. The changes in cast and characters feel honest, as though a lot of thought have gone into them. Even with the character mentioned in my spoiler, as much as I hate to see said person go, it makes sense and doesn't feel dishonest or like a cheap tactic. I'm going to miss that character a lot; it's going to be tough filling their shoes.