The subject is scientific, so it sounds like e.g. "what are disadvantages of complex numbers". I am not talking just about science. I mean the whole purpose.

Such discussion will have no effect on people, who truly know what functional programming is. It also may have incorrect or misleading effects on people, who don't fully understand, what functional programming is.

To expand on Ranger's point, the OP's question is specifically requesting people's anecdotal experiences and opinions concerning applied knowledge. Science is the repeatable process of discovering and accurately modeling nature (for varying definitions of "nature").