I really enjoyed reading about Daniel Tammet and his book (Born on a Blue Day) is fascinating, but I'd hesitate to describe him as 'ordinary'. He's likely somewhere on the autism spectrum and also has synesthesia which affects his perception of numbers (amongst other things); his relationship with the world is going to be very different than for most people.
He had one epileptic event in his childhood which may be why he was called 'ordinary.' The confound with autism of course makes the 'ordinary' designation hard to justify though (as you suggest).
