I'm glad this thread has come about because I was going to start one on a similar theme myself. I'm starting a detailing business and was wondering if I was taking too long to detail a car, but it appears not.
Like the general consensus seems to be, it all depends on the size, shape and condition of the car. I also find that the amount of exterior trim it has a big factor in how it takes!
For example, my 1 Series with minor swirls and no exterior trim took 4/5 hours for a full exterior detail, whereas my Mum's Freelander with trashed paint and heaps of exterior trim and a high SUV roofline took 10/11 hours for a full exterior detail.
As Burlyq says, detailing is a skilled profession and people need to be aware of this. If somebody wants their car was/waxed they can go elsewhere as I'm sure there will be somebody who'll do it in an hour for $10, but I'm more interested in achieving perfection, and it's by doing this that really puts the satisfaction not only in my eyes, but also in the customers.
Ben