Chuck's introduction seemed alright, although when in the train, it seemed like Lee was about to meet his maker when Chuck began approaching him. I like Chuck for many reasons, but the Omid and Christa introduction seemed a little forced (Especially with the whole "They're coming with us and that's that." dialogue options).
Even when Christa disapproves with your prying, and states something along the lines of "Not being a part of the group for too long." she still tags along. For being a loner, with her boi, Omid, she sure opted to come along, Walkers be damned. As for those two, Christa seems decent, but Omid seems a little too "helpful." I'm not the biggest Christa and Omid fans, just yet. :P Yay, Charles!