Right now, Duplex's call-in reservation skills are limited. It's only useful for restaurants at the moment, and it requires a bit of effort to be sure you get time and seats you want. VB also noted that some restaurants simply wouldn't take reservations, even if they had public numbers and didn't limit bookings to the web. You may still have to talk to a human, then.

It's a start, though, and it shows that the technology can work in the real-world. The larger challenge may be scaling it until it can work reliably for a variety of services, across many cities and devices. That will depend in part on business owners agreeing to talk to an AI. If many of them decline, Google won't have much success no matter how well its technology works.