I have gained on some and lost on others. I think it really depends on how much of a hormone you were on. The tricky thing with b/c is it is tricking your body to think you are pregnant, that is why some women are prone to weight gain while on it. However, coming off it, your hormones need to stabilize out again, making it a risk.
I guess the biggest issue I would be worried about gaining is if I got knocked up lol