A friend of mine who was doing his driving lessons told me he was having trouble getting it in gear. He'd go into 3rd instead of 1st or 2nd instead of 4th etc. I let him loose on LFS and explained how he should be gear changing with the flimsy G25 gear lever - by following the shape of the gate with smooth movements without forcing it across and essentially guessing and hoping it's in the right gear. A couple of days later after his next driving lesson he told me how the explanation and experience on "that game" helped him a lot, he no longer had trouble changing gear.
Also from personal experience, when I took my car off road a while back I experienced some severe under steer. My experience with LFS kicked in and helped me make a choice on how I should proceed to handle the situation - without that experience I would have been left to make a quick unexperienced decesion and hoped for the best.
Does it make you a better driver? I would have to say no.
Does it teach you techniques, concepts and driving theory? I would say yes to an extent.
Does it effect driver/driving behaviour? Define "behaviour". Are you talking drivers attitude towards driving or drivers reaction to certain events? I would say both are entirely dependant on the individual. Some may think they are god and do silly things while others may not. Some may utilise common strategies from their sim experience into real life situations while others may not.
A simulator can help your understanding but that is no substitute for real experience, and even then 20-30-40 years experience doesn't mean you are a good driver. In my opinion some drivers I have been with whose had years and years of experience are completely crap drivers - tunnel vision, lack of observation, tail gating, inconsiderate manuvering etc. Although, these people I consider crap drivers have a clean driving history and they consider themselves good drivers....
All this is dependant on the individual concerned. For some people a simulator can help, for others it can't. However regardless of that, experience has to come from somewhere.