As an instructor I just cringe when I hear a hear a person say they have used MS FS before they started ab intio flying lessons. It is simply not realistic enough to teach skills which can be wholly transfered to the aircraft and encourages a host of bad habits, the most vexing is the habit of flying the aircraft by reference to the instruments instead of referencing the natural horizon out the windshield. MSFS has a lot of utility for a licensed pilto who wants to practice instrument procedures, but IMO it results in negative learning for ab intio students.