I seem to remember reading somewhere that the Gradient_Bump node in P7 is only there to support the 'old' style .bum bump map files, so you don't have to convert them to jpgs to plug into the Bump node.

If my memory is letting me down again, can anyone explain what the Gradient_Bump node is for?

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)