The nice benefit for my sight reader was getting a bit of a come-uppance with a 50% on his second ever spelling test. He was not pleased, and after looking for blame realized it was on him. Wasn't really anything before spelling which required intentional effort for him to learn. (not counting his writing as that is a different sort of learning)
As to reading, dunno how to measure that. We know his first word was "Comcast" ~20 months (yum, irony.) I would likely way underguess the number of words he knew by three (>500?), but because of his vision he couldn't much follow words on the page to read a story until the beginning of last school year.
