Annoyances: the City-State slider is disabled on some maps, including both Earth maps. That feels like a pretty needless limitation. But I dunno. Maybe I'm just weird about my dislike for the City-State stuff, at least when there are 12 of 'em hardcoded into my game. Little guys just get in the way.
...honestly, I think City-States would work better as "minor powers" or whatever, since they always have way more territory than necessary. An actual city-state should only use one tile, or as few tiles as possible. Oddly enough Beyond Earth may have gotten this right with its outposts.
Observations: Aussie culture bombs are far more useful than their Polish counterparts, maybe even a little OP, since they're tied to the relatively common pasture improvement which, chances are, you'd usually build out of habit anyway, while I've rarely felt any need at all to build forts. That said, I guess its power relies on your map type and the random seed, so it won't always be super overwhelming.
The Aussie's Outback Stations have a neat visual effect, combining all nearby pastures into one, which I like a lot. More importantly, the Stations have yields which scale upwards by era, which is a first, I think. So they're probably always useful.
Oh yeah, and the bonus yields for districts scaling to coastal appeal seems pretty powerful too. Not that anyone would settle cities inland on the Australian continent, but yeah, this is a pretty powerful Civ for island maps or anything with nice long coastlines. Probably sucks if you roll Aussie and get stuck landlocked on a pangaea or something though.