When Microsoft has launched Windows 8 they had made lots of changes to its UI like they had removed Start Button from taskbar and introduced new Start Screen. This Start Screen is introduced by keeping touch based device in mind.
Many users has liked it very much and took it on hand but there are many users too who doesn’t liked this Start Screen want their old traditional look back.
It will be very helpful to those users who still wants to stick with keyboard and mouse, but other features like Hot Corners, Charm Bar and so will be there in traditional UI.
To recap from leaks till now, Windows Blue or Windows 8.1 will be a complete new OS which will still use Live Tile UI, it will allow you to customize Start Screen completely, lost of changes has been made in settings to make it more mobile friendly.