A family member booked. A driver committed. The wait got shorter. Then it got longer. And longer. And then our trip was cancelled without reason. Another was booked. Same gig. We had no opportunity to 1-star those drivers for being dicks. The third arrived but we didn't get the fabled offer of foot massages, nor were we plied with snacks or drinks. It was just a cab ride with the awkward "You've been great passengers, I'll rate you five stars!" exchange at the end. "Err, thanks mate?"
The return trip was pretty similar. It's 1am. Want to go home. One dropped. It's getting really cold now. Second arrives. Again, an entirely standard private hire experience with the added convenience of being asked to rate at the other end.
But this lack of recompense for crappy initial service isn't good. If a real private hire did that, you'd use another company and would never use that one again. You'd tell friends and family not to use it. You'd be able to complain to the council about the company. With Uber, you just huddle up and hope the next is better.
This is by far one of the more benign complaints you hear about (versus deliberately slow routes to push the top end of the range, or surge pricing) but it absolutely undermines the purported convenience factor. Being able to talk to a manned rank in actual contact with their drivers is so much better in practice.