Air quality is still absolutely horrible in China, but the streets are clean, the trains are spotless and incredibly convenient, and even walking around dark alleys after midnight felt safe. My biggest problem is that scammers targeting foreigners are common, but I suppose it beats the more in-your-face or straight up pickpocketing/mugging you'll find in non-East Asian major cities.
The progress of China in terms of infrastructure and economic development really something incredible. I know people who worked there under a decade ago and said it was an absolute wasteland and still have that idea today, but everyone I know who goes there now (myself included) feels like they're getting a glimpse of the future of the rest of the world, for better and worse.
If it weren't for the restrictions on personal liberties, I'd gladly pack my bags and move there longterm.