I take mine mostly for the reduction in heart-attack risk. One of the major complications of high blood glucose is cardiovascular problems. Add that to my already RICH family history of every male member of my family having MI's (myocardial infarction, aka 'heart attacks') in their 40's, and I want to take every precaution possible.
And I'm not exaggerating ... if I make it another 5 years without any cardiac events, I'll be the first male member of my family to do so in 4 generations. My dad has had 3 now, and in December had his 2nd bypass surgery. His brother died of a massive MI at 46. My grandfather (my dad's dad) also died of an MI in his 40's. I'm hoping regardless of some time spent being overweight that my current and previous athletic conditioning helps prevent that from happening.
In addition to shanny's link, there's also an excellent article
here.