Hi Amy,
I've had good results at 2,000mg of met. Before that dosage, my cycles were long and erratic (37-76 days); since increasing it (I was on 500mgs for a few months), my cycles have been 25-27 days.
I just saw my endo today, and she said that in her experience, women seem to see the best results at 2,000mgs. It seems like 1,500 is a common dosage; but a bit more may make a huge difference.
I've been fortunate to not have the awful met side effects; in part, b/c I've always been on the extended relesase version of the drugs (Metformin ER and Glucophage XR). In part, I think I've just been lucky. My endo told me that even with the extended release meds, a lot of women have troubles getting up to higher doses, and miss out on the benefits.
Hope AF shows soon for you. I know just how frustrating those long cycles are.
GL!

Lissa