Hard thing to get used to:
(At least in a crowded city with crowded public transportation)
Smells. Every person seems to smell strongly of something applied to heavily, and unlike when we are all in cars on US freeways or in larger stores instead of tiny ones, one is closely subjected to all of these aromas. Perfume, aftershave, and worst of all cigarette smoke from all the pedestrians who walk along breathing this out into me as I pass.
It's something I can't stop noticing, being that in the US I lived in a city where, apart from being in a store, I wasn't around masses of strangers in close contact, or maybe even the strangers I was around just didn't go in for lots of perfumes or aftershaves or didn't smoke cigarettes. Austin was very health conscious therefore smoking was low-incidence, certainly out in public. And being a very casual city, men didn't splash on the cologne, and perfume was only for a special night out. You just didn't really get to smell these smells over there.
It's a bit overwhelming now. In the US I never noticed men swimming in aftershave or women sending perfume smoke signals to the next county, but here I do and I'm finding it very irritating.