28 days later had alot of originality in it. While it's premise is tired and over done at first glance, it's style, it's characters, it's look at the objectifying of females should the world ever come to an end. All these things made it incredibly different. Also the zombies in the movie were unlike any others I've seen.
Now to the whole, "are they actually zombies" thing. Obviously, they are not zombies in the traditional sense, they are not dead, they are not rotting, they are technically alive. But, they are obviously zombie like creatures, they are walking humanoid creatures who no longer have control over what they are doing, and are no longer concious. They are following pure instinct, just like zombies in other movies. The only thing that seperates them from the traditional zombies is the fact that they aren't dead, although, it would be arguable that they aren't really alive anymore, since they aren't concious. This is why i consider them zombies.