Brandon Chester, writing for AnandTech, digs into the macOS Sierra beta. Before you dig in, remember that this is a beta, and an early one. Keep that fact in mind as you read. Also realize up front that Brandon did not update his Apple Watch to the latest beta. As he says in his conclusion:

By this point I’ve covered many of the tentpole features of macOS Sierra. Right now it’s a bit difficult to test some of the other features announced at WWDC that relate to continuity between macOS, iOS, and watchOS due to the fact that all these platforms are in beta and, in the case of watchOS, a beta that you can’t return from. Unfortunately, I feel that those features end up being the most interesting ones, because they’re only made possible by Apple controlling the software and hardware stack across all their devices.

That said, I found this an interesting read, as AnandTech reviews inevitably are.