People with PCOS are already susceptible to Insulin Resistance anyway. The BC is just so we can regulate our periods so there are LESS cysts on our ovaries, which is good for me. They hurt sometimes. I think as long as you stick to a low GI diet along with the BC (though I've been off of mine for over a year) you shouldn't have to worry too much about IR.
I got on BC to regulate my periods. I would go months without one. I was on it for 2-3 years I think and when I got off of it, I had slightly heavier periods but I haven't missed one. Which makes me wonder if it trains your body?