I've been told by my PPL instructor to cut down with using flight simulator as you pick up bad habits for example. When I first got taught how to land, and in my first few circuits, I was flaring far too high as my mind had trained my brain to do this automatically from flying 747's on flight simulator. My instructor could actually tell and asked me after a landing "Do you use flight sim?" etc etc
I personally dont think its very realistic flight wise, you cant feel a thing for a start lol. I use it to practise checklists now, when I'm trying to memorise them etc, but thats about it. Flight sim still is very fun tho!