Hi,
I am a type one (have been for 25 years) and currently on metformin.   I only started taking it in November last year and so far so good.  I was struggling with my weight and with a calorie controlled, lower carb diet I have lost 10 lbs since taking it.  Beforehand I was dieting and exercising and my weight always remained the same.  My blood glucose readings are lower and I am now taking less insulin.  It can make you feel a bit sick and nauseous but increasing the dose slowly helps.  I realise that it does not suit everyone though, so I am lucky that it suits me and I feel better on it.