I find what is stressed in this discussion is very important : that the progression from BTD to GTD and maybe finally to Swami should be smooth, if possible, excepted of course if a serious health issue necessitates to be quickly dealt with.
When I first discovered the BTD, by reading ER4YT, at the beginning of April this year, I got caught by Dr. D's enthousiasm about what can be achieved throught the diet (like many people, I assume) and I found myself quite hungry to learn and do everything... asap. Of course I did read his advice to integrate changes little by little into one's life but it's like I just couldn't do it.
As a complete beginner, I searched for support and advice and first went on a french internet board. There, someone urged me to read GTD and answer the questions helping to choose between BTD and GTD. It turned out it should be GTD for me. So I bought the book, measured myself (wrongly, at first, because I was too much in a hurry) and changed my diet again before I had had time to integrate the one for A's.
As I'm thinking about the past seven months, I realize that the transition from BTD to GTD has been too rapid. I'd have needed more time to accustom myself... not only to a new diet but to a totally new concept: the one that different blood groups determine different metabolisms. To me, this accounts for the deep annoyance I experienced at some point (when I found out that according to Swami I was an Explorer rather than a Warrior). It took me time to understand why I was so annoyed while just a few days earlier I was quite happy and excited on reception of Swami and when I ran it for the first time.
However. Things happened the way they did and I did learn a lot in a short time. Still, if I could start over again, I believe I wouldn't switch from BTD to GTD so quickly but I would take the necessary time to learn and integrate the theory as well as to go over my general knowledge in nutrition again.
I think that the persons who stress that there is no hurry to quit BTD if it is satisfactory provide newbies with good advice.