I found this site while googling ESFP and registered so I could comment on this thread.
I'm clearly an ESFP in real life, have in the past belonged to the IQ clubs Mensa and Intertel (top 2% and top 1%), and so far in college I've received straight A's (including in the so-called "N" classes such as English lit., philosophy, logic and math). My ex-boyfriend is clearly an ESTP and has a masters in civil engineering from Stanford University. Even though neither of us has the special N that seems to be needed for intelligence, we've managed to stumble through both our N and S classes.
My husband is an INTJ, has a B.S. in math, and he turns to me for logic issues. I was the top student out of a class of 30 in my college logic class. And btw, that doesn't automatically mean I'm an NT, it means I prefer ESFP but have a higher IQ, per tests, than my husband. He has gifts stronger than mine in other areas, including carrying projects through to completion.
Upon meeting me, the first impression is of someone bouncy, emotional, silly, always on the go -- the typical ESFP. It doesn't mean I'm not intelligent, it only means I don't use intelligence as my preferred way of dealing with the world -- I use Se and Fi, with the IQ-type of intelligence a secondary preference. I wonder how many so-called non-intelligent ESFPs are in the same situation I'm in -- showing one side, having the other hidden.
Here's one example of a weakness... Though I can understand everything said, I can't, on my own, go as deeply into ideas as some N's when it comes to such subjects as English lit. I can keep up with the best when it comes to the precise meaning of a piece of literature, but that's it, after a few pages I've said what needs to be said and have trouble picking up on some of the nuances.
I don't know what the average IQ is of ESFPs, but to look at them as stupid until proven intelligent is insulting to potentially millions of people.
Anyway, nice to meet everyone -- or almost everyone.