I've been researching cycles smoke simulation, materials and rendering a lot lately, and this is the shader for smoke and fire that I've come up with. It produces defined smoke without losing much detail (my original shader lost detail), as well as blackbody fire. The test scene is like in the picture: wineglass, inspired by Blenderdiplom's smoke in cycles demos. The smoke behavior could use some work. I've also added a small amount of compositing to the scene. Test this shader in different conditions and let me know what results you come up with.