Well from an Instructors point of view we have seen to many times issues come up due to MSFS use.
We have also seen students have to pay alot of money to rectify issues caused by using Simulation in a none controlled self taught manner.
Some times the issues are masked by sheer natural ability and only come to light when the work load gets increased to single engine NDB apparoach level. Sometimes it only comes to light during type rating or line training. Unfortunately its not impossible to fail a type rating. I know 3 personally that have done so. 2 at the sim stage and one doing the base check after 2 additional hours doing circuits he was a first time pass as well at IR. He was apprently fine doing apparoaches at 80 knots cruising at 130knts. 170knts clean circuit speed reducing to 120knots with 10 times the amount of power that he had had previously and he couldn't manage it.
Its really not a snobbish recomendation to be extremely careful with your exposure using it. Its just we have all had not one but many students which we have had to battle to break out of MSFS induced habits. Its always easier to teach someone as a clean sheet than have to clean that sheet or correct that sheet before imprinting the training thats required.
In reality the SPA/MEP/IR is a high work load test of potential. It allows you to then go forward and learn. A fresh out of school IR is a danger to themselves which only experence can then sort out.
Even at my level (whch isn't high to be honest) I am very consious of my experence limits. A multi crew icing approved turbo prop with a 201 hour FO in the RHS fresh out of type rating no problem whazzing around europe. Put me in a MEP single crew these days (and to be honest it was the same when I had just passed the IR and never changed) and I would be a fish out of water. Yes I would know what I was doing round the procedures these days but all the additional PIC skills required to fly that aircraft safely wouldn't be third sense.
The only reason why myself and Billiebob are saying be very careful is purely due to what we have seen pilots go through. You will find that instructors that used it personally themselves during training quite quickly change thier opinion once they are in the RHS teaching.
The most common lesson I give in line training these days is effects of controls and straight and level. And getting the pilot to let the machine do the flying and not to annoy it and take it out the groove. Unless the sim has a trimming feature which needs constant analog adjustment with changes in speed its pretty much useless for training.