Hi! From my own experience, during the ppl stage, flight simulator did not really help any more than regular "chair flying".
But I am now about to start my IR and, even though I have MS flight simulator, it makes my computer so slow I don't use it. I have instead purchased an IFR trainer pc simulator from cockpitweb.com which is really just a panel with all the instruments (no fancy scenary, it is not necessary), but it all works very well, you fly it with a regular joystick and the program gives you exercises to do like the real IR syllabus, then you can see what you actually flew versus what you should have flown. Hoping it will save me some time on the sim!!
just my 2p's worth.