The second preview is now available for all of you who want to get a peek at 4.10. Even more fixes are included in this update and there are still more changes to come. Come try it out and give us your feedback about the new developments!
To get started, head to the "Library" section of the Unreal Engine tab in the Epic Games Launcher, select "Add Versions", and choose 4.10 Preview 2. If you already have Preview 1, then just upgrade when you are ready.
For more information on the fixes included in the release, check out the update from Stephen Ellis on the Unreal Engine forums, and be sure to read up on the known issues list. As a reminder, the Preview builds are for testing only, and should not be used for the active development of your project.