You've long had the option of scheduling Uber rides, but that didn't necessarily guarantee your fare. It could cost you a pretty penny if there was a surprise surge at the time you hopped in the car. That won't be an issue going forward -- Uber is now locking in fares when you book a ride at least an hour in advance. The price you see is what you'll pay at the end, even if traffic snarls would have resulted in paying more. This could be more than a little helpful if you're booking a ride to the airport, or expect to travel downtown during rush hour and would rather not pay extra for the privilege.
The feature is currently available across the US, and kicks in automatically depending on your scheduling.
This comes over a year after Uber started offering guaranteed fares at the time a ride starts. In both cases, there's a clear goal: Uber wants to eliminate the uncertainty that might lead you to take a rival ride hailing service or (gasp) a taxi. If you know exactly what you'll pay, you may be more likely to take Uber again knowing that your costs will be predictable.