I'd agree to that, and solving problems in FP always made me think harder to get an elegant solution. Though, it also means that you're uncomfortably close to math. I think to fully exploit/understand FP, the programmer also needs to be good at understanding the mathematical models/formulas behind FP. Otherwise, I think he cannot truly exploit the potential of the tools he's using. I haven't spent a lot of time doing FP to justify that opinion fully, but whatever FP I did made me wish I took my math classes more seriously.