Ever since Brecht announced his work on a new GPU-powered renderer Cycles, it's been the biggest buzz in the Blender community that I've seen in a long while. If you need to catch up, check out this useful FAQ by DingTo.
It’s amazing to see the great images people are already producing with it, keeping in mind that the Engine is still in “Alpha” stage. So, it’s not feature complete yet and speed will be improved as well in the future. Based on own knowledge and infos Brecht and Ton put online, here are some answers to common questions I stumbled upon while reading various Cycles discussions