I was a precocious reader (<3yo), and I have a strong suspicion that kids who learn to read early read differently than those who learn "on schedule". I think early readers do something much more like code breaking, and I wonder if this affects second language acquisition or other skills. I don't necessarily think one style is preferable to the other, but I do think there is a potentially interesting difference.
I was very happy to read early, and I think it was advantageous for me, but I have not seen evidence that early reading in itself provides any lasting advantages on average. There may be a good deal of heterogeneity in the early-reading population.
"Code breaking." Interesting. I think I agree. I learned to read around 4 years old, and I did so by trying to follow along and predict words as my dad read to me. I can recall thinking "ok, there is a word coming up that looks like 'be'" and then verifying it was correct when he read it. I taught myself in that fashion. I can recall passing a road sign and reading "tippecanoe" aloud and surprising my parents shortly thereafter.
When we taught our own kids to read, I was surprised that this was not the way that they would learn to read. We ended up having good success with hooked on phonics with our first two and the last one did well with vast amounts of repetition and memorization of his favorite books.
I was very happy to read early, and I think it was advantageous for me, but I have not seen evidence that early reading in itself provides any lasting advantages on average. There may be a good deal of heterogeneity in the early-reading population.