Joby Pro Sling

Is anybody using the Joby Pro Sling for carrying camera and lens? I am finding the weight of 1D4 and 100-400 lens hanging round my neck is not too good. I have read good reports of the Joby Pro Sling and was wondering if anybody has in the field experience of this piece of equipment. Information and observations very welcome.

No personal experience Black Rapid seems to be the big boy in town. Having said that I just googled it and it seems to have happy owners. I note it has a carabiner which would be a very useful safety/precautionary feature, i.e. no chance of the lens becoming detached and falling to the ground.