First of all, I have to state I work for a company that makes flight training devices, so take the following words in that vein.
It depends what you mean by simulator first of all - do you mean a (FAA) Level 6/7 Flight Training Device (FTD) or a Level D Simulator, or a JAA Flight Navigation Training Device (FNPT) or an FAA Advanced Aircraft Training Device (AATD)?
Each has it's own level of fidelity and is intended for different things.
An AATD or an FNPT is going to be good for teaching skills in general, but not specific to a model of helicopter. IFR training, or learning to hover are general skills. And these devices can be excellent for learning those skills. As a former test pilot for a major manufacturer stated - "No helicopter pilot should be in a real helicopter for the first 10 hours"
Since we're just getting devices like this into general circulation, they haven't had the impact on training that they deserve.
For FTD and Level D simulators - they are designed to duplicate exactly the handling and performance of the real thing - or at least they should. They are designed to replace flying time in the real helicopter for the purpose of getting a type rating (another subject for US operations). So they should be pretty exact as they will train things like muscle memory. If the performance for the Category A takeoff discussed before wasn't accurate, then someone should say something. You'll be learning negative things in the sim...
end of rant...