Sorry to gatecrash your thread, but I have taken Metformin, twice.
It does indeed play havoc with your bowels. Its best to introduce gradually, 1 tablet a day for a week, then 2 for a week, then 3 (I was on 1500mgs per day). I found that I got "stuck" on 2 for a couple of weeks, my body just couldn't cope with 3, but I got there eventually. You need to take them 3 times a day, morning, lunch and evening, not, like I tried this time round, all in one go! Don't worry if you find it hard to move up to the next level, just give it a couple more days.
I had the metformin in conjunction with clomid the first time round, resulting in DD (3.5) and this last time, on its own while waiting to see my Fertility Consultant - baby is due in January (I only managed to get to 2 tablets)! So, in my experience, it is a wonder drug! It has the great (in my opinion) side effect of helping you loose weight.
I hope you don't mind me butting in, but I was sort of left in the dark the first time I was prescribed it and advice was very helpful.
Good Luck