Agreed. I think it's pretty hard to not know what it's like to feel stupid at least some of the time. Even most geniuses are 'stupid' in at least one area. Most of us have felt the sting of seeing a colleague, friend, or stranger pick up a challenging topic with enviable ease.
The more interesting question is, what it's like to feel that way all the time. I suppose we all choose to associate mostly with those of approximately equal intelligence to ourselves, so we're probably mostly oblivious to our relative intelligence.
Well, for one I know I'll never write any spectacular piece of software that will really make a difference. My only half-decent contributions were to port a library from one language to another.
As you rise in rank, you are associating with people who are all of higher intelligence. I made whatever i could on dint of twice the effort and reading a lot more. I am fortunate I was able to save enough money since i reached a stage where I knew i could not continue to be employed. I was too old to be a continue at middle management, and too stupid to move to higher management. I've retired and lead a slow life living on savings. I do programming for fun, but no-brainer stuff.
Sometimes I do think i am blessed with stupidity. Most intelligent people i know are miserable, spending their entire lives chasing wealth or becoming something to be happy.
I've often considered myself a genius at being stupid. My stupidity aptitudes are staggering across all categories.
Fortunately this has lead to some spectacular failures and the burden of knowledge that comes with. I think I've successfully managed to leverage my multiple stupidities effectively.
The more interesting question is, what it's like to feel that way all the time. I suppose we all choose to associate mostly with those of approximately equal intelligence to ourselves, so we're probably mostly oblivious to our relative intelligence.