I use this feature a lot, especially with getting my son to school with his broken leg. It's a great feature and Uber have been extremely reliable. In fact they are usually early.
However one thing I have noticed is the variable cost. If I order a day or more ahead it is always $24. However the same ride, scheduled on the day or on-demand is usually quite a lot cheaper at around $15. I'd much prefer to get that, tip the underpaid driver $5 and still be saving ACC $5.
It seems that scheduled rides are fixed, but I wonder if they are subject to surge pricing?

