None So Blind is a good little story based on the old saw that we only use some small portion of our brains, and that this can be enhanced significantly. Neuroscience and psychology have advanced a bit since then--brains actually do grow new cells, every day, and we do make use of most of our brains most of the time. But it's a nice bit of speculation, taking on several different prejudices and assumptions in the process. I would give it 3 stars.
But if you really want a good story of this nature, check out Ted Chiang's Understand. It's a powerful first-person piece, and somehow manages to convey what it's like to be so much smarter without sounding stupid.