3.6 totally broke my site couldn’t login now having to FTP, i got to the point of trusting wordpress updates not to bork the install, now im feared I can never trust them again. I dont have time in life to investigate why wordpress updates dont work, this is a matter of trust, 3.6 was a disaster for me.

the update overwrote my entire includes folder with 0KB length files, no idea why ? re uploaded fresh copy of includes folder via FTP and attempted to login then updated database, things back to normal but crikey … hope this helps someone.