I like commuting on my backup bike since I'm less worried about getting it stolen. My primary bike I save for pleasure riding although lately I've been commuting on it more and more (and locking it up with a heavy chain + u-lock). When the snow flies it will become my only bike due to its belt drive, IGH, disc brakes, and my one set of studded tires. If it breaks down I'll get a ride or take the bus until I can fix it, or ride the backup bike if Mother Nature smiles and provides a spring day in the middle of winter.