Windows 10 build 10074 is released and available for download from Windows Update. The biggest change has to do with Cortana, Microsoft's personal assistant. There's now a sidebar from which you can access Notebook, Reminders, Places, Music, Help, and Settings. There's a little animation when you launch Cortana from the Start menu.
64-bit English USA Win 10 Professional build 10074 in ESD format: http://b1.download.windowsupdate.com/d/updt/2015/04/10074.0.150424-1350.fbl_impressive_CLIENTPRO_RET_x64fre_en-us_6171fdb41101598d83604fd6c0bb4a51c0a88913.esd
Conversion tool to convert the ESD file to ISO: http://www.tenforums.com/tutorials/2570-esd-iso-create-bootable-iso-windows-10-esd-file.html
64-bit English USA Win 10 Professional build 10074 in ESD format: http://b1.download.windowsupdate.com/d/updt/2015/04/10074.0.150424-1350.fbl_impressive_CLIENTPRO_RET_x64fre_en-us_6171fdb41101598d83604fd6c0bb4a51c0a88913.esd
Conversion tool to convert the ESD file to ISO: http://www.tenforums.com/tutorials/2570-esd-iso-create-bootable-iso-windows-10-esd-file.html