Some of the highlights:

• The New Sky Model has better overall tint to the lighting in daytime, and supports the sun being below the horizon for dawn/twilight effects
• New Lens Effects give you vastly more control over bloom & glare
• 78 new materials in the Corona Material Library, including new Flooring, Carpet and Ceramic Tiles categories
• Avoid texture repetitions with updates to the UvwRandomizer
• New Adaptive Environment Sampler removes the need for Portals, saving you the time (and pain!) of setting those up, while giving more accurate results
• Support for foam in Phoenix FD
• And more!

Read full details about all the above, plus everything else there isn't space to mention, over in the blog post.

For those of you who have tried Corona before and your 45-day trial expired, we've automatically refreshed the demo period to give everyone an extra 14 days so you can try out all the new features! Simply download and install Corona Renderer 6, and you can activate the refreshed demo period right from within 3ds Max. Enjoy!