Apple yesterday released OS X 10.9.3 with support for 4K displays, contact and calendar syncing improvements, and more



From MacRumors:

Many (but not all) users are, however, experiencing a bug in the update that hides the /Users folder. The /Users folder is a top-level folder that contains the home folder and personal files for each user on a Mac. It's not clear why only some OS X users lose access to the /Users folder, but the inability to browse this folder could be problematic for some Mac owners affected by the glitch. A range of solutions for the bug have been suggested with varying degrees of complexity, with perhaps the simplest noted by Kirk McElhearn and Chris Breen of Macworld: Launch Terminal (/Applications/Utilities), enter "sudo chflags nohidden /Users", and press the Return key. You’ll be prompted for your user password. Enter it, press Return again, and the Users folder will be visible as it once was.This solution is not, however, a permanent one, as the issue will reappear if the machine is restarted and the fix will need to be applied again.

  OS X 10.9.3 Bug Hides /Users Folder for Some Users