Once it was over, my first reaction to it was "stupidest movie I've ever seen".
And it wasn't because of the idiotic movie science - I work with real viruses for a living, if I got upset at every way movies and TV series don't match reality, my blood pressure would probably have killed me by now. The thing to do, for me, has always been to just shrug and move on, and maybe laugh about it with the co-workers over lunch.
The actual problems were the following:
1. A very good beginning, completely wasted.
2. Weak and predictable plot.
3. No meaningful character development.
4. Plot threads - such as they were - left to wither and die with no resoultion.
5. What little point there was to the movie was rendered meaningless by the useless ending.
6. Not enough action (never mind good action) to make it enjoyable as a mindless zombie flick. Those blood-spewing rage victims are scary the first time you see them, by the end of the movie they border on unintentionally comical.
I actually thought Spiderman 3 was better, because it at least had a couple of genuinely fun action scenes, though I suppose if you look at wasted potential, perhaps 28 Weeks comes out ahead after all...
Oh well - there's still Pirates of the Carribbean 3 to look forward to - I liked the second one, even if it wasn't as good as the first, Johnny Depp is always a trip as Sparrow, Geoffrey Rush is back as Barbossa, and if all else fails, it should at least have some fun action scenes. Oh, and the monkey. Monkeys make everything better.