Hot on the heels of the Mac OS X 10.6.8 build Apple seeded to developers earlier today, Lion Developer Preview 3 was seeded to all developers. Though the update shows up in Lion's Software Update as "Lion Developer Preview Update" it is not a fourth update of Lion Developer Preview 2, but is a completely new version 3 build.
All Software Update says about the new 1.07 GB build is that "The Lion Developer Preview Update is recommended for all users running Mac OS X Lion Developer Preview 2." However, MacStories has confirmed that some of the new features in Developer Preview 3 include a new boot animation, new graphical elements in the Finder's toolbar, new desktop wallpapers and that Reading List is now enabled in Safari.
Apple OS X Yosemite