I saw "28 Days Later..." last night, and I enjoyed it quite a bit. The premise was a little far-fetched, but that's expected when you lay down your $7.50 for a horror flick. I'm not going to summarize the plot, and I'll try not to spoil too much, but you may want to stop reading if you don't want to know what happens.
Ok then. Far-fetched premise: a virus that's passed through the blood turns humans into mindless killing machines (zombies, if you will) 10-20 seconds after infection. Not likely. The infected people then spend most of their time lounging around, waiting for uninfected people to walk by so they can infect them. What's with that? Why don't the zombies fight and eat each other? No explanation.
The movie isn't scary in the traditional horror sense, but it is rather spooky. The opening scenes with Jim wandering through an empty and deserted London are eerie, and the zombies' appearances are sudden and startling. The cinematography is excellent at times, but distracting at others, and borrows somewhat from "Evil Dead 2" and the like.
The end is a bit cheesy, but there really wasn't much else that could be done considering the hopeless situation the characters were in. The first half of the movie should have been doubled, and the second half should have been eliminated. Overall, I'd recommend the movie; although it isn't incredibly scary, it's spooky enough to give kids nightmares.