My doc (who is a bit alternative thinking her medical practice) suggested this diet a couple of years ago. I tried it for several months and did lose a fair amount of weight during that time. However, as I have done with every diet, I researched and studied each diet suggested for the various blood types and found them all to be relatively healthy, higher fiber, lower calorie diets, overall.
Personally, I think there is no magic in the Eating Right for Your Type diet. I think it's just a matter of the diet being relatively "healthy" that makes it work.
I'm a type A, and I found the mostly vegetarian diet too limiting and difficult to follow for the long term.