a photo of your commutator....?
But seriously, whilst you can commute on... well... more or less anything, in nice weather, when the days are long, IMHO a proper grind-it-out commuter bike has mudguards, lights (removable winkies are OK in town), luggage carrying capacity, should be corrosion proofed, and preferably have a low-maintenance (or 'disposable') transmission. It should also be unattractive to crims if you need to lock it up anyplace.
I found that if I ever used a 'nice bike' for commuting (secure bike parking at work...), I'd be reluctant to nip into a shop on the way home because of the security worries.
cheers