I believe practicing in LDs can help in the waking world, but only if you're already capable of doing whatever the activity is. Someone so uncoordinated that they can't dribble a basketball won't become a professional by practicing in LDs.

Now, someone that is already good at basketball that practices in LDs, I think that will help them a little--the more you do something, the better you'll get. Of course it won't suddenly make them the greatest, but it will help in more subtle ways.

About what Orgun said, that makes sense. A surgeon that LDs about surgeries would become more familiar with what to do, as it's essentially practice on what he/she would have to do in their waking life.