Cycles Rendering

• Volume Rendering:
• Rendering with cameras inside volume meshes is now supported
• Cubic voxels interpolation is a new option helping to avoid artifacts on low resolution smoke simulations
• Faster rendering of homogeneous volumes
• Support for GeForce 9xx GPUs
• Improved rendering with area lights
• Viewport specularity for the viewport is now also implemented for Cycles
• And more!

User Interface

• A new fullscreen mode without any buttons or other "annoying" elements to improve the UI
• The 3D View got an option to display the world background right from the viewport
• Pie Menus:
• Confirm Threshold to confirm a pie menu without releasing the original key
• Nested Pie Menus (a Pie Menu within a Pie Menu) are now supported
• Chinese and Japanese complex character input:
• General support for Input Method Editors (IMEs) has been added
• Only supported for text buttons for now
• Only supported on Windows and Linux for now
• Supported is Sougou (Chinese), Bing (Chinese), QQ (Chinese) and Microsoft integrated (Japanese)
  And now guess why we have a Chinese Splash! ;)
• And more!

Modeling

• Knife-tool:
• Cuts can now be created using free-hand drawing
• Cut-loops can now be closed by double click
• Selection:
• A new selection method "Select Similar Regions" was added
• You can now skip adjacent faces while using the select more/less function
• And more!

Sculpting/Painting

• Texture Painting:
• The Add Simple Uvs operator for texture painting now uses a simpler unwrap method for better quick UV layouts
• Face-mask edges are now hidden to give proper visual feedback while working with masks
• Brushes:
• Changing brush size, detail size and strength can now be done using numeric keyboard input
• Brush strength can now also be changed for Grab and Snake Hook brushes

Sequencer

• A Backdrop similar to Compositor is now implemented for the Sequencer as well
• Strips:
• Strips can now be snapped to other strip's start- and endpoints
• A new slip Tool allows moving content within the strip itself
• And more!

Freestyle NPR Rendering

• Freestyle got a new SVG exporter, implemented as an add-on
• View maps can now be cached
• More options for chain selection and chain sorting were added

Animation

• Grease Pencil (which got a major upgrade):
• It is now possible to edit and animate strokes (!!!)
• New draw styles were added, e.g. filled stroke interiors, volumetric strokes, ...
• The Grease Pencil's user interface (which is now completely defined via Python) has gotten a general overhaul
• Two quick access pie menus were added
• Graph Editor:
• Revised the set of operators for showing/hiding curves from the keyframe area
• Circle selection for Curves was added
• And more!

Add-ons

• Collada Importer:
• Importing rigs previously caused problems with leaf bones (end bone of a bone chain) so a fix was created for that.
• Added an experimental bonechain Finder to predict the longest possible chains of connected bones.
• The FBX Add-on now uses some advanced handling/tweaking options for importing and exporting armatures
• The Copy and Paste Add-on is now using version 2.0

More Features

• There are a lot more features that are new in Blender 2.73, so make sure to check them out!

Feature Videos

• Look at many of the above features in the Blender Developer Sneak Peeks - a video podcast series that showcases important milestones in the development of every Blender release.

Bug Fixes

• As for every Blender release, hundreds of bugs were fixed, thanks to the hardworking Blender developers.