Pros

  • Retina display support
  • Overall performance improvement on compatible Macs
  • Faster importing, especially for Raw shooters
  • No cost to upgrade
  • AVCHD video support
  • Cleaner user interface
  • Improved editing tools
  • Unified library structure for iPhoto/Aperture

Cons

  • Requires Mac OS X 10.7.4
  • Some may miss advanced Highlights/Shadows sliders