Lamictal has really helped ease my depressions. I don't think it's reduced the severity per se, and I don't think it's stopped my rapid cycling, but it's definitely lessened the duration of my depressive episodes, which is awesome. Now my depressions are a week long or shorter!
I will probably have to find another drug to help lessen the severity... but Lamictal has worked out pretty well for me. Hope it works well for you too.