I don't know about drinking coffee, but could the correlation with smoking just be because smokers die earlier than average, and hence never get the time to develop Parkinson's?
You've got a valid point. It took me about a year to become really proficient in python, but after that a month to pick up C relatively well, and another 3 months to pick up Scala (probably because functional programming was something new to me). But after Scala, Haskell took about a week, so you might be on to something with similar paradigms being easier to pick up.