Mina, I'm glad you brought up the blood type diet. It was one of the many resources I discovered along my health journey. Ironically, I was looking into ayurveda at the same time and I was amazed at how closely they lined up! Certain doshas in ayurveda tend to be certain bloodtypes and the recommendations for eating in each discipline match up with almost spooky accuracy. And ayurveda has been in practice for thousands of years!
I'm blood type A and sure enough, almost all the foods the blood type diet A (and the Pitta-Vata dosha) says to avoid are foods that I don't care much for and steer clear of naturally. Most of the foods recommended by both were already staples for me. I experimented back and forth, added a few spices here and there, and bingo, I had a delicious diet. Shortly after that, I went vegan--which, frankly, wasn't much of a jump by that time.
Since then, I've gone back and forth from vegan, raw vegan, and vegetarian in order to work out some kinks. I found the kink: I was dangerously magnesium deficient. Turns out, once you are seriously magnesium deficient and under a lot of stress, there is no way on earth to get the megadoses of magnesium necessary to balance again from plants alone. That's why I was craving diary and meat so bad and getting ill on a vegan diet--my body was desperate for mag. So, supplements. And they're working--Yay!
I'm going to take a few months to equalize and make sure I'm actually absorbing what I'm eating now (one of the many things mag regulates), and then try raw vegan again. I still follow the blood type diet and ayurveda for the most part because it works so well for me. Statistics and medical tests are worthless to me if I wasn't in them; I always conduct my own test, I call it "eating."

The blood type diet has a load of great information in it and I learned a lot about how the circulatory, endocrine, and the gastrointestinal systems rely on one another. As you said, you don't have to adhere to the diet tightly to get a huge benefit from it. It would be interesting to learn how blood type lines up with ectomorphs, mesomorphs, and endomorphs, too, because ayurveda sure does!
Baby Herc, a gorgeous mesomorph pitta-vata A