Mine adores her leash walks. Cats are naturally skittish animals, being both prey and predator. So if they trust you as a source of protection the comfort of walking without worries is a benefit that outweighs the restriction of the harness. Plus it's high quality bonding time.

I live in an apartment complex with lots of animals and I see several of my neighbors leash-walk their cats regularly.

It just takes some time to train them usually. It's much easier if you get them used to it early in their lifetime, though.