The WinSxS folder is used to store install and uninstall files, windows packages (current and previous versions of a component) and out-of-band releases. You should not completely delete this folder, nor will windows let you.
You will find this is one of the largest folders in your system, and particularly if you use SSD drives like me you will want to keep the data stored on the drive trim.
To remove unnecessary backups, make sure SP1 installed, and open a command prompt using Run as administrator.
Run the command: dism /online /cleanup-image /spsuperseded
After the operation the WinSxS folder has reduced from 11.3Gb to 7.6Gb