On Wednesday, Uber's self-driving cars hit the streets of Pittsburgh, as part of a pilot program available to up to 1,000 passengers. The Ford Fusions seem to respect speed limits, and stay in their respective lanes, but it's clear that there are still many kinks to work out.

Over the past 18 months, the ride-sharing giant has spent millions on its autonomous car project, based out of Pittburgh's Advanced Technologies Center. Earlier this summer, Uber acquired Otto, a startup that makes self-driving technology for trucks, for $680 million. Still, the company faces competition from companies who are are also working to develop autonomous cars--including Google parent Alphabet Inc., Tesla, Mercedes-Benz, and Infiniti. Last month, Google unveiled its own ride-sharing service, Waze, in San Francisco, offering cheaper rates for carpools.

So far, reviews of Uber's program launch have been generally bullish. The New York Times's Mike Isaac wrote that stops and turns were "near seamless," and that he felt safe for the most part. On the downside, he noted the car failed to start for 10 minutes, and that it drove particularly close to cars parked on the side of the road. In a Wall Street Journal review, a vehicle "jarringly hit the breaks" at one point. And later, after encountering a large truck parked in the middle of a side, a human driver was forced to take over.

Pittsburgh, which is laid out in triangle form, is notoriously difficult to drive in. There are sharp grades, dozens of tunnels, bridges, and potholes. But the self-driving cars come equipped with sensors and recording equipment, which Uber says should help gather more data "about what makes drivers and riders comfortable and safe," says Emily Duff Bartel, a product manager at Uber's Advanced Technologies Center.

For now, chronic worriers fear not: The cars come equipped with an eject button that allows passengers to end a ride from the backseat.