Microsoft is continuing to push out new Windows 10 Desktop builds, the latest of which -- Build 10061 -- is available today to Windows Insiders on the Fast Ring and via Windows Update.This is the first new public Windows 10 Desktop build, which runs on desktops, laptops and tablets, that Microsoft has made available to testers since March 30. That Windows 10 Desktop build, 10049, included Microsoft's new "Spartan" browser (as well as IE 11).
A couple of Windows 10 Desktop builds have leaked in the interim, but Microsoft hasn't made any of these available as an official public preview. Microsoft also did not release 10049 or any more recent Windows 10 Desktop build to the Slow Ring of testers, and has no plans to do so.
The new Windows 10 Desktop build released on April 22, includes a number of fixes, plus several new features. According to a blog post on the newest build, Build 10061 includes the new Mail and Calendar apps; improvements to Start, Taskbar and Action Center; improvements to Continuum, the switching feature that makes moving easier between Desktop and Tablet mode; Task View improvements; and Virtual Desktop improvements.
Microsoft has fixed an issue that blocked users from enabling Hyper-V with Windows 10 Desktop in this build. It also fixed various mail indexing and Spartan bugs.
There are known issues in this build, including the inability to launch Win32 Desktop apps from the Start Menu.
Microsoft released a new test build of Windows 10 Mobile for Windows Phones on April 21. That build, 10052, was all bug fixes and no new features.
Microsoft is believed to be planning to launch Windows 10 at the end of July 2015.