Truly self driving cars would allow you to participate in other activities safely while the car moves you. You could read a book, play a game, apply your makeup, etc. Given that trade-off, I think most people would be willing to sacrifice the extra 2.5 minutes a trip.

2.5 minute estimate derived from the difference of travel time between half the average US daily travel of 42 miles at a speed of 60mph and the same distance traveled at 68mph.

Most people would accept the trade-off of being in the car 5 minutes longer per day if it meant they got 42 minutes of leisure instead of 37 minutes of weaving through traffic.

Also with a critical mass adoption of self-driving cars the speed limit could be increased.