I have done two track days with my car at Watkins Glen in the past year and a half or so, and this past time my instructor was specifically telling me how shocked she was that I had only been on a real race track once before that time. Sims are not perfect in the physics department, but I knew exactly where I wanted my car to be at all times on the track and I was able to put it there. She also commented that I did a good job of staying on my own line through turns and not following the car in front of me when they would take a different(and usually wrong) line, this is something I think I definitely learned from sim racing without even really thinking about it.
Just to comment on something Intrepid said, I'm sure everyone's brains work differently, but at no time on the real track was I thinking to myself what was different being there in real life as opposed to the sim. I just don't see how that would ever even cross my mind, there's too much else going on to be thinking about a video game. In fact, I mostly learned stuff about the line at Watkins Glen in real life from the instructors that I take back to iRacing when I'm running laps in the sim.