Interesting that this question has thrown up such strong feelings in response. I am another one who was taught to read by my dad, based on the methods in this book. He tried it just to see if it worked. It does work at such an early age. It's not pointless, and I am glad that I learned to read before school made it seem so boring... I've seen my boys go through 'reading schemes' bringing home book after book with one word to a page and they just weren't interested.
However, I think it was difficult when I started reception already knowing how to read anything I wanted, as the school really didn't know what to do with me. Eventually I was allowed to borrow books from the junior library but I think it was only after quite a struggle. You only have to search mumsnet or the wider media for studies on adults who were labelled 'gifted and talented' as children to find that sometimes, having developed abilites earlier than the establishment expects, actually is a hindrance in being able to function well in wider society. But then (to the OP) if you learned using this system yourself, you know how it's affected you. I think the school's attitude is quite key but unfortunately lots of schools aren't very well set up for children who are G&T (whether labelled as that or not).
Also, having started to use that system with my boys and then stopped, I think Glenn Doman is quite prescriptive and that you don't necessarily have to follow the steps to the extent he says. In fact, even he points out early on in the book, that young children try to learn to read even if they aren't being exposed to flashcards. My ds3 (just turned 3) loves our local supermarket sign as the supermarket name starts with the same two letters as his name. The name is printed at regular intervals along the outside of the supermarket and I frequently have to hurry him along as otherwise he'd spend ages sounding out each word over and over.
Having read not only the Glenn Doman book but also quite a few books by John Holt (I particularly recommend 'How Children Learn') I tend to lean on the side of letting them discover words and reading when they want to, rather than sitting them down with flashcards up to 9 times a day as the Teach Your Baby to Read book seems to be suggesting. I do like the home-made books, though. I've made books for all my boys and they come back to them even when way past that stage of reading, because they are so personal. I think I even have the books my dad made for me somewhere.
Hth a little :)