Scenegraphs?

hi! i''ve read sufficient articles on scenegraphs. i have yet to try the OpenSceneGraph library, but right now am learning up Java3D which is totally scenegraph based. Even some game programming books employ scenegraphs in their object oriented approach. my only attempt at using scenegraphs previously is in a simple game GUI for an assignment. The only reasons i used it is to simplify adding GUI elements (addChild, removeChild, etc) and primarily automated management. i like how the render calls and cleanups can be initiated at the root and propagation causes all children nodes in the graph to shutdown in order from leaf to node. in my experience, it worked like a charm... a lot lesser code! my real question is actually how much are they used in real life game development for instance? more importantly, the heavy reliance of inheritance and virtual mapping MAY be considered a performance issue by some. but do those really matter?