I just loaded Blender 2.71 yesterday, and the first thing I did was jump right into playing with fire in the Cycles Rendering system becuase I wanted to see how easy it was to set up light interaction between the fire and objects in the scene. It worked like a charm, but it took a lot of setting up, and tweaking. However, the results were stunning, even on my first couple of tries.
You could not do this until now with Blender, that is, have fire give off light that could cast shadows, light up space, and be reflected while rendering in Cycles. In fact, this new feature is so new that there was only a few people who posted some guides on the web to get you going in Blender, but even those scraps of information was hard to follow through and figure out how to use it on my copy of Blender, and that most of my time was just playing around with it before I figured it out. But the more I played with it, the better the results I wanted. Now I am working on some animations, really having a blast with this! I may stay up all night working on this. 🙂