From reading around (was looking to get it done on our B7 2.0 TDI a while back) it seems like its mostly snake oil. It MAY clean off a little bit, but the majority will still be sitting there and for a proper clean you need to get it walnut blasted. The walnut blasting seems to be more something they do in the US with the TFSI engines which are known for getting full of carbon deposits on the intake.
Other than walnut blasting there is always some elbow grease, a de-greaser and a toothbrush, obviously when doing the ports on the head you need to ensure the valves are in the CLOSED position. Oh, and I have seen YouTube videos of people using fire + compressed air to clean out the intake manifold and it DOES work...just don't try it on a plastic intake.
You can see a video of the fire + compressed air method here.....