All the machinery of functional programming languages that's creeping into non-FP languages is great. I actually think that FP one-liners are usually _more_ transparent than the corresponding non-FP loop.

However if I'm not mistaken an important point of FPLs was to eliminate side-effects and that the ultimate goal was program verification (not validation). I.e. you could prove a program correct in the mathematical sense. That seems still a long way off.