The workday would be 4 hours: 2 hours at dusk, 2 hours at dawn with a quick break around midnight for running around, screaming for no reason in particular. The rest of the day would be naps.

They'd have wares if we had coin.

Every human invention is about efficiency: making communication easier, killing people easier, extracting resources easier, more food, more leisure time, more comfort. We have put thousands of years of innovation into being more lazy about everything.

Meanwhile, cats sleep 20 hours per day and have humans to clean their box and fill their food dish.

Domestic house cats have already reached levels of evolution humans can only dream of.

There wouldn't be any vegans.

I recommend the documentary "red dwarf" about what happened to cats left alone for 3 million years...

Not much different. Humans serving cats, that's what we have now as well.

There would be no mountains. They would have knocked the top of them off a long time ago.

Shady dealers hiding in the alleyways selling nip. Cats sitting on the curb nipped out of their minds rubbing the ground and batting at dust motes in the air. Social service workers with vials of Nipcan at the ready to treat overdoses.

The nip epidemic is out of hand and there’s national debate over incarcerating or treating nip addicts.

The simple answer here

note: Gaiman in case that's a problem

First off, I would think that in order for them to get that far they'd have to evolve longer, grasping fingers like ours, or maybe they would have designed objects to work with their paws, but without the fine motor control afforded by fingers I'm not sure how they would invent anything.

There would be a lot more meat production and no crop farms, since they are obligate carnivores, but this does assume they don't evolve beyond that on their way to domination.

I suppose humans wouldn't have evolved past being apes, it's unlikely they would want us as pets, so we're probably either hinted for sport or as an exotic food source, or largely ignored.

It's possible that animals would be going extinct at an alarming rate, since cats hunt for food and fun, and as a society they would require more meat.

It's hard to know it cats would make the same mistakes we've made, but I would think it's safe to assume they've lost touch with their kinship with nature or largely ignore it, like humans do now, so perhaps a lot will be the same. I don't know if they'd give in to greed like humans have, or create a system that's more beneficial overall. If the former, work would be hell for them, it would probably be a 3-4 day work week, but that would be rough for them just like our current system is for us.

The biggest changes would be anatomical, I think. Their fur would thin out, except on the top of their heads, their tails might grow shorter or disappear to allow them to stand and walk upright, the breasts in females would grow larger and the number of their offspring might reduce to one or two as their gestation and childhood periods get longer to account for higher intelligence.

Have you ever seen a cat play with their food? I don't think I'd want to live there

No more birds

No stairs, elevators or escalators. Open concept building with lots of landing areas.

more laser pointers

In a word: very.

IT WOULD BE ALL TIARAS, DIRTY SHIRLEYS, AND REVOLUTIONS.

Nothing would get done because the cat people would be too busy napping.

They would make us all carry can openers 24/7 for the immediate gratification of our cat overlords.