, Google’s self-driving car project, hit another milestone on Wednesday by launching an Uber-like service in Arizona that’s driven by a fleet of autonomous taxis. But there’s some caveats to the service.

The service, dubbed Waymo One, will ferry a group of riders that have participated in the company’s autonomous vehicle pilot program since 2017 around a roughly 100-square-mile zone across four cities in the Phoenix area—Chandler, Tempe, Mesa, and Gilbert. The catch is that, now, they’ll be paying fares. And as Waymo describes it, the service works a lot like Uber and Lyft.

Riders download an app, provide a credit card number, and plug in a destination. Images of the app, published by Waymo on Wednesday, show a setup that’ll be familiar to users of the other, better-known taxi startups.

“Riders will see price estimates before they accept the trip based on factors like the time and distance to their destination,” Waymo .

While generating revenue through the deployment of autonomous taxis is indeed a milestone for the company, the service won’t include that were seen tooling around the Phoenix area previously. At least for now.

“At first, Waymo-trained drivers will supervise our Waymo One vehicles,” Waymo wrote.

The technology isn’t flawless, either, demonstrating just how far the industry has to go to achieve the envisioned future of driverless cabs ferrying people around to any destination they choose. In a test run with Reuters, one of Waymo’s taxis as “slow and jerky at times.”

But even in these favorable conditions, Waymo’s technology performed much like a student driver: slow and timid.

The vehicle was hyper-aware of pedestrians and had trouble distinguishing their intentions. For example, it stopped for a man standing at a crosswalk talking on his cellphone even though it was clear that he was not going to cross the street.

The car slowed well ahead of stop signs and drove at a snail’s pace over speed bumps. Yet it sometimes executed lane changes with an unsettling jerk as an automated voice over the speaker system called out “left” or “right.” That is a feature Waymo says helps riders understand what the car is doing.

Still, the vehicle pulled off some impressive feats, Reuters said, like “crossing three lanes of oncoming traffic to execute a left turn into a parking lot.” And the safety driver at the wheel “never touched the wheel during the entire drive,” Reuters noted.

The price for a ride is also similar to competitors, at least by estimates described by Reuters and . Both news outlets described taking a three-mile trip that cost around $7, in line with fares offered by Uber and Lyft for the same drive.

It’s a super impressive feat to get these cars on the road, and I’m sure many couldn’t even have expected we’d be here even a decade ago. And Waymo told reporters it plans to eventually introduce the fully driverless taxi setup into Waymo One, so the completely futuristic experience of a self-driving car without anyone at the wheel could be available to the public sooner than we think.

If you’re in the area, and you’ve tested out a Waymo One cab, we’d love to hear about the experience. Drop us a line at [email protected].