I have a iPhone4. I use iCloud for my personal calendars. Work uses Exchange and I am not allowed to sync a personal device to it. I use Mail on my work laptop and sync it with the Exchange server. I then use USB to sync my phone with my laptop to add my Exchange entries to my phone. That is until I updated to 6.1 today. I seemed to have lost today's Exchange entries, but the rest of my entries seem to still be on my phone.