Once you have more buffers (files) open than windows in Emacs, then having a quick way to cycle through buffers is invaluable. Even with 4 windows open, I still find myself using IBuffer,
C-c C-x, many times.
Sometimes I just want to switch between the current and previous buffer in the same window. So this is how I tweaked my Emacs configuration (based on Emacs Live) to cycle through buffers.