You mean the 3100 right?
Surely removing the af motor greatly increases costs because instead of paying a bit mote for the body you're now paying 50 quid more for every lens you buy? I'd rather buy a body with the motor if it will save hundreds of pounds in lenses.
The D3200 came out a couple of months ago, but everything up to the D90/D7000 doesn't have an inbuilt AF motor.
Nope. Basically having the motor in the body means that you end up having to have a motor that can focus every lens, which means that it's both really loud and fairly slow, and that you can't override the autofocus as there's a disconnect between the lens and the af system. It's not a very expensive component to put into a lens as they know exactly what the motor is moving, and has the advantages of speed, full time focus override and low noise when focusing..