Looks good. Doesn't feel good. Simulation isn't the real thing...and I design simulations
What is interesting is that I ran LS in GT before I did in person. It actually didn't help at all, and in fact may have had some aspects of negative training. However once I ran the track in person, I was much better on the game.
The problem comes in the amount of physical feedback that you use when driving at the limit. The visual cues (which simulation does well) diminish in comparison to the physical cues (which simulation does poorly or not at all).