Been using Shimano SPD for a few years now, my commute is 16.5 miles one way.
A few nice features with 2 bolt systems(SPD, Speedplay Frogs, Eggbeaters, etc.) that
make them convenient for commuting - flat shoes makes it easy to walk, double sided
means no flipping(Crankbrothers 4 sided), usually not too sensitive with dirt/mud/snow:

https://www.youtube.com/watch?v=FFyX...IoDLA&index=57