They aren't great, just another proprietary browser. Every time I've used it has been sub-par. It reminded me a lot of Opera in that it was very opinionated, even if it tried to offer some feature. Apple makes money off of apps, not websites, though, so it makes sense they don't invest much into their browser.
I’d never use it due to lack of uBlock Origin and good dev tools, but it’s hard to argue with the speed and battery efficiency on macOS.