I went with friends and liked the movie more than I expected to (I probably wouldn't have seen it on my own).
Agreed. I went into the theatre with very low expectations and was surprised. In fact, I liked it better than Superman for which I had very high expectations after all the hype.
Regarding the scent thing, I thought that was a clever way to solve the problem. And as one of the characters points out, animals have the same natural instinct to not feed on sick prey.
But it goes back to "how sick is sick enough?" What ailment did the gimp guy in S. Korea suffer from that made him "immune." Does "cancer" (or whatever the bald, reedy kid in Israel had) or "oldmanism" (or whatever the old man in Israel had) really smell that different enough than a cold? And why would ANY infection or disease matter to a creature that's already dead and not biologically active?
Again, the cold, the flu, virtually ANY disease or infection can be "deadly" in the right circumstances. So wouldn't the zombies pretty much ignore the vast majority of the population? And even if you're not suffering from a viral infection you still "have" every one you've ever had, you're just immune so it doesn't make you sick anymore.
That plot thread doesn't hold up under much scrutiny. I *liked* it because it was an interesting take on things and if they go ahead with more movies it'll be interesting to see how the build on it but it's not something that holds up under much thought.