The problem I had with full on functional stuff was seeing what the point is - ok you could replace your for loop with some weird recursive stuff which the compiler will turn back to imperative behind the scenes so it will run quick but I had a trouble seeing why. However replacing some javascript loops with underscore stuff I was able to see how it was more compact and less bug prone. Also it doesn't take long to get.
The problem I had with full on functional stuff was seeing what the point is - ok you could replace your for loop with some weird recursive stuff which the compiler will turn back to imperative behind the scenes so it will run quick but I had a trouble seeing why. However replacing some javascript loops with underscore stuff I was able to see how it was more compact and less bug prone. Also it doesn't take long to get.