I like the fact that the Rage Virus doesn't actually create undead zombies but is instead a super rabies. It solves a lot of the technical issues around zombies. I like that whatever can kill a person can also kill a rage zombie. It's also cool that you can actually just starve them out.
28 days is really an unnecessary amount of time for the rage zombies to die off though. A hunger strike can last that long but that is only with a person consuming enough water. 3 to 4 days without water and you are dead. Especially if you are projectile vomiting blood.
As for actual movie stuff: I think the premise for each movie is pretty unique. The soldiers in Days aren't there to clean up the infection "by any means necessary". They just want women to live with. Weeks is the only Zombie movie that deals with resettlement that I can remember.
I didn't like: the Rage Zombies are too random, aggressive, and intelligent. The Days military base is under constant swarm attacks which doesn't make any sense. How are the zombies finding the base and then coordinating swarms? The Zombies also shouldn't be busting through doors walls, and windows like they do. In the Weeks the military should have been more prepared.