Never actually wondered until now (don't know why): 5GB+ of OS? What the hell is in there? A huge driver DB to support all mobile hardware out there?
Checked my Samsung and JB is reporting apps separately from the OS size. The total space starts at 9.23GB for a 16GB model, even worse it seems.
Knowing that Android is based on SELinux, you can have full desktop / laptop OS installs under 5GB. So really, what adds up to this 5GB behemoth of compiled libraries and code?