I love my PC!!
Bought it to correct scratches in the hood of my black Blazer.... not so good at scratch removal, even going down to Meg's #4 and a cutting pad, but does it ever make a difference compared to hand application.
The week before I bought the PC, I had done the whole car with Deep Crystal cleaner, polish, and Gold Class wax. When I got the PC, I repeated the same process on the hood and front fenders.... That's been 4 weeks at 700 miles/week, 4 hand washes and 4 touchless machine washes ago, and I can still tell a big difference between the front fenders and the doors.
Helped a friend today do his new Avalanche(black) with Meg's #2, #9, #7 and Zymol cleaner wax and it took about 4 hours for the two of us, including washing and claying. Still got some wash scratches, but looks great !
I seriously doubt you could do all this by hand in 4 hours.
It's not a miracle machine and can't do everything a rotary buffer can, but it's practically impossible to screw up your paint with and does a great job applying waxes and glazes.
My trial and error as far as speed is concerned is that the thicker the product(cleaners, swirl removers) use faster speeds, waxes and glazes slower. I move the machine slowly and half-lap passes, regardless of product. A detail spray between cleaners and glaze and a final machine buff with a water mist and a MF bonnet really seemed to work well.
My humble $.02 worth,
Bill