I ride a road bike fitted with a Nexus-8 hub. It's great. I can and do keep up with everyone. I did 3 century rides on it this year. Efficiency loss? How much does someone with a derailleur lose when they fail to downshift before coming to a stop? With the hub gear you just click it down a couple of gears while stopped and ride right off when the light changes. In 5th, on the Nexus, you're in 1-1 which is as efficient as it gets. Any I never have any loss due to a poor chain line. Maintenance issues are almost non-existant.

No, it isn't what you'd ride in a time trial, but you wouldn't do well commuting or running errands in a real race car, either.