UDK is Unreal Engine 3 – the complete professional development framework. All the tools you need to create great games, advanced visualizations and detailed 3D simulations. The best tools in the industry are in your hands.
The Unreal Engine impressed me many times. I love how nice it runs, even with high definition textures and a big amount of high poly models. Also are the tools in the UDK very user-friendly and the live-preview, the ability to play while coding, is very useful and speeds everything up. I hope that this engine will get even better in the future!