This is a great thread! Newbies often ask where to find more testimonials.
I started the BTD mainly because of joint pain, but also for weight loss. I was very lucky that I found it in my early twenties, not long after I began looking for ways to lose weight. I hadn't 'dieted' much at all before that, yet with short trials of calorie restriction I knew that wouldn't work, as I'd usually gain weight the more I cut back on calories. The blanket advice "just eat less and exercise" didn't quite work for me. Exercise did make me feel better, but pre-BTD it didn't help me lose weight.
I soon experienced rapid weight loss, an end to chronic sinus and bladder infections, much less joint pain, no more eczema, better cholesterol readings, my creeping (109) blood sugar started behaving normally again, and I had more energy. Most of these benefits lingered for quite some time even when my compliance level dropped for a couple years. Some weight came back on slowly, with the help of a pregnancy and nachos, but this year I renewed my compliance with the addition of non-secretor restrictions, and my weight is back down, my stomach feels much better, and I'm much more aware of my food and how it effects me.
I also credit the diet with helping me (and my MD) diagnose and treat h. pylori and celiac disease. Thanks be to the BTD Encyclopedia, and those words that now define part of me: O non-secretor.
Oh, I almost forgot to mention that the BTD helped me get off antidepressants after 4 or 5 years on and off them.