These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Awesome Music: "In the House, In a Heartbeat," a steadily increasing anxiety attack of a song that perfectly matches the climax.
Broken Base: Go up to a group of fans of this movie and ask one simple question - 'is 28 Days Later a zombie movie?' Then stand back and watch the ensuing punch-up.
Ending Fatigue: For "surviving the apocalypse" movie fans, this movie starts off great but then makes a hard left midway through, sticking the main characters with the soldiers who take the forefront as antagonists and carries a different tone to match.
Christopher Eccleston (who was also featured in other Danny Boyle films such as Trainspotting and Shallow Grave) went on to play the Ninth Doctor and is known as this for British audiences/Who fans. Americans would know him as Destro in the GI Joe live-action film, and Claude from Heroes.
What an Idiot: The activists who free the monkeys in the lab at the beginning. The scientist even tries to warn them that they shouldn't do that, but of course they do it anyway. Especially the girl who releases the monkey, who is "thanked" by being bitten and becoming the first human victim of the rage virus.
Even if they weren't infected, the activists just freed them without any form of protection. Did they intend to carry wild animals with their bare hands?