I have PCOS with Insulin resistance (just tested negative for diabetes). I have taken Metformin to help control my crazy irregular cycles. I have taken it on 2 different rounds now. The first time I took it was about 8 years ago. I took it for a few months along with clomid & progesterone & all kinds of other stuff. After just a few months, I was sooooooo tired of the GI side effects, I quit taking it and left it all up to fate. I moved to Colorado a couple years after that, ate a little better (although, not much at all) and walked a few times a week. I also found an awesome beginner belly dancing class once a week. Anyhow, I lost about 25 pounds in a year. It's not a lot to lose but it was just enough and I got pregnant on my own. Irregular cycles and all. I just started taking it again recently because my little girl is now 5 and after 5 years of trying, we still have to brother or sister for her. I am easing myself into the meds this time so it doesn't effect my GI as bad. One reason is to help try to regulate my cycles (which it did do last time) but also to hopefully help me process my sugars a little better and lose weight. So far, no luck for anything. But it hasn't been long this go.
Good luck on your journey! :)