WM, since BMI is calculated by using weight, I should think it is relevant. Besides, the link I gave refers to the BMI for an assessment of body fat from height and weight. Hence, if you want to lower your BMI you either grow your legs or lose weight!
A BMI of between 18.5 and 24.9 is considered normal weight by the NHLBI. 25-29.9 is overweight and if it is over 30 then you would be clinically obese.