I thought 28 Days Later... was great. A breath of fresh air and a thoughtfully entertaining horror flick. So it's not lightly that I say that I think 28 Weeks Later is even better.
The only thing that's missing from the original is the parallel between the rage virus inflicted attackers and the brutality and rage of the main male character and his enemies, at the end of the movie. Everything else is just as good, or improved.
Well, everything except the one specific zombie who seems unnaturally intelligent and obsessed with two characters in the movie. Super Zombie didn't fit at all into the "rules" of the movie, and seemed like an unnecessary plot device. That minor complaint is virtually my only one, though.
28 Weeks is brutal, intense, and more frightening than its predecessor, with the scenes in the crowded parking garage and the pitch black subway tunnel REALLY standing out. The simple story moves along briskly, with no superfluous moments to distract from the tension. The tone is understandably different (there is a new director, after all), but I don't think that the slight change hurt the movie at all. I loved the cast, and the ending is one of the best I've ever seen in a movie of this kind.
Any time that I feel like a movie went by too quickly, I know it's a fantastic one. And that's exactly the impression that 28 Weeks Later left me with, even the second time around. It's less deliberate and more action-focused than 28 Days, but only the most stringent fan of the first movie will have an issue with that.