i3wm is the best thing since sliced windows, but the default config file contains some poor defaults.
This isn't my i3.config, but it contains all of the critical "must-have" alterations that I am always recommending to people who see my i3 setup and go "wow, I have tried tiling window managers before but I never realised they could actually be great!".
All modifications are annotated with #/
This version is based on the default config emitted by Ubuntu 15.04.