From Unity Technologies:
Unity is the development environment that gets out of your way, allowing you to focus on simply creating your game. With Unity you can assemble and tweak your levels at the speed of thought. Edit, test, and play with Unity, this lets you drill down to find the fun, then polish it until it is perfect. Unity brings beast light mapping and umbra occlusion culling to the table a key part of making games look great and run fast across all devices. Design the perfect aural ambiance with our new integrated audio filters and in-scene editing tools.
What's new in this version:
Version 5.0 adds physically-based Standard Shader to make your materials look consistent in any lighting environment, cross platform; Real-time Global Illumination, built on Geomerics Enlighten technology; Audio Mixer, to massively improve audio in your game; HDR Reflection Probes to enhance visual fidelity; PhysX 3.3 to bring massive performance improvements to 3D physics; Major updates to the animation system; WebGL preview.