The first scene is very amateur (poor make-up, acting, etc.). After that it improves.
I really liked the overall sense of the world that was conveyed in many ways. Some survivors were highly organized, some had gone completely rabid (supporting the infected or just preying on other survivors). How everyone shares news/rumors with anyone they meet.
The interaction of the Man and Boy was also well done. The Boy develops throughout the story, with brief scenes showing how the Man is constantly training him. The ending, although abrupt, ties in nicely with the openning. Also, after you think about it, it just seems like the logical outcome.
In all, a very well thought out post-apocalyptic movie done on a very low budget.
Extremism in the defense of liberty is no vice. And moderation in the pursuit of justice is no virtue.