Msofts blog on this update to Windows 8.1 is well worth a read:

fwiw its worth mentioning a couple of improvements from 8.1 RTM:

Amongst other things Update 1 intelligently boots users without touchscreens to the desktop by default and uses desktop apps by default, it reduces the sensitivity of hot corners, highlights newly installed apps and dramatically improves the Modern UI for keyboard and mouse users. It also cuts its install size in half (from 32GB to 16GB) on SSDs, runs faster on slower hardware and drops minimum memory requirements from 2GB to 1GB of RAM.