What are the disadvantages of using a flight simulator to train pilots?

It is much cheaper (and safer) to let a fledgling pilot crash in a simulator than to crash a real plane while learning the nuances of flight.

1) the invaluable flight hours without the cost of fuel and flight maintenance 2) simulation of life threatening situations (no power landings, stuck gear) without the actual loss of life 3)...

No, Combat Flight Simulator 3 does not need a Flight Simulator.

Typically the compass rose. Some systems use a heading tape instead.

Trains are not always the fastest way to travel. Some trains only run once every few days and may not stop where you want to go. Subways can be noisy, cramped, drunks can cause hassel, stangers...