There has been a huge amount of pilots having problems with simulator sickness in various armed forces.
Unfortunately, the simulator concept was already implemented in the governmental planning-so it HAD to be a good system..
For that reason, all studies about simsickness showed that there are up to 60% of all pilots (flying in a simulator) suffer from simsicknss-starting with minor appearances like dizzyness that only last for minutes up to severe "flash backs" up to 4-5 days AFTER simulator flights (life threatening if you are driving your car and you loose your balance TOTALLY for a few minutes...
There are a lot of studies-but no one seems to find a "cure" for these symptons.
One theory says that is the difference in the "seat-of-the-pants" feelings and the impressions on the body and sensoric organs....
That could explain why mostly experienced pilots have problems in the simulator-because their bodies/brains already KNOW how it feels, when a helicopter is doing a turn, for example...
In a simulator, you cannot simulate EVERYTHING.
If you´re using a hydraulic movement system, the system has to neutralize itself when reaching a certain extension.
Even if you do not SEE this movement, your body FEELS it-and that leads to disillusion...
There is an interesting study by Dr. Kolasinski from the US Army Research Center, called "Simulator Sickness in Virtual Environments", written in 1995.
Just try google...