Me and most people in my immediate family speak 3 or more languages fluently. Still, in my non-scientific observations I've noticed little difference between say, multilinguals and monolinguals when it comes to tasks not related to well, speaking languages. It seems to me that in actuality monolinguals usually speak one language with greater fluidity since with multilinguals you are constantly mixing up the languages all the time to greater or lesser degrees.
Is is quite rare (I can only think of one occasion in my life), where I have listened to an articulate and intellectual communicator / speaker, who was not monolingual in whatever language they were speaking.
I think being multilingual has advantages - you can speak multiple languages :) but beyond that I have often wondered if it is really as advantageous as scientific news media makes it out to be. Would you be just as well served by spending your energy building in your workshop, playing music, painting, studying mathematics, etc?