Glad you asked!

  • Completely redesigned user interface including single window & full screen support
  • Completely rewritten audio system
  • Significantly improved arrangement & mastering features
  • Notification Center (10.8 and later)
  • Auto Save & Versions support
  • Multi-Touch gestures
  • Fully AppleScriptable including Audio Units
  • Fully 64-bit
  • Effects groups
  • Effects automation
  • Scrubbing
  • Audio hardware output & channel mapping
  • Full support for iXML
  • Loop Bar
  • Brand new meters (à la Spectre)
  • Advanced iZotope MBIT+ dithering and SRC options for disc burning
  • Session-at-once (SAO) & Track-at-once (TAO) modes are selectable for disc burning
  • Advanced Ogg & FLAC export settings
  • Import WavPack, Musepack & Monkey's Audio
  • Grid offset
  • Changes to Audio Units modify the document (on close, you will be asked to save if a change occurs)
  • UI Improvements including improved drawing & zooming
  • Support for Retina displays
  • Vertical grid

...and many, many more!