+1000 for the tiling window manager comment! I can't stand the weird nightmare which is macos desktop management with spaces.
iCal is a big draw though, Linux calendars are terrible and since thunderbird choked and left xul Mailmate is attractive too.
So, by using Linux, I lose, I dunno, iPhoto and iCal and whatever, but I gain real Linux with a real Linux package manager and immediate access to the latest version of every tool I can imagine. Plus fun stuff like BTRFS, a tiling window manager, and a feeling that I'm actually in control of the system I spend 8 hours a day in front of.