Excellent stuff Martin. This is actually very usefull then, as originally I thought it affected the overal Density of the cloud shape rather than it's transparency, which I realise go hand in hand, but this Final Density Shader is going to come in very handy.
I'm currently rendereing a 'new approach' to cloud forming, which atm with six buckets half way looks promising. Might have to reserect my Cloudbusting Thread.