First, Windows 8.1 Update 1 is designed to run great on more devices, providing faster access to the things that matter most to you, and a more consistent, better experience across both touch and non-touch devices. Yes, that includes universal apps for PCs and phones!
Second, the user interface has been improved for mouse and keyboard lovers, with taskbar access from any screen, and the ability to pin Windows Store apps to the taskbar alongside desktop apps and website favorite. IE 11 will also automatically detect the size of your screen and type of device and optimize itself for the best browsing experience possible.
These improvements provide faster, more direct access to the things people care most about, so activities such as powering down, searching the Web and switching between apps are easier than ever. Navigating with the mouse and keyboard will feel more familiar and intuitive because there’s more consistency with where controls are and how they work.
New, lower cost devices will also be better served by Windows 8.1 Update 1, thanks to the 1GB of RAM, 16GB of storage minimum requirements.
Windows 8.1 Update 1 will be a free Windows Update for all Windows 8.1 users, and a free Windows Store update for all Windows 8 users starting April 8, 2014.
Update: Also available via MSDN and TechNet.
I'm looking forward to both the Windows 8.1 Update 1 fixes and the new features, how about you?
Source: Windows Experience Blog