No doubt, Metformin or any other drug has no lack of studies and opinions to back it up. The same has also been true in the past of Vioxx, Avandia, Fosamax and just about any drug you can think of. That is, after all, where the money is that pays for such studies and opinions.
I will concede that Metformin appears to be less dangerous than most drugs. However it is still a drug and I stick to my firm opinion:
If nature did not intend it to be in your body, it probably shouldn't be.
That is indeed my opinion. One that is shared by most true advocates of natural health.