First of all, I never buy bikes or frames unless I know that they will fit me well. That is always the top consideration. I also have an eye for aesthetics and only buy bikes that I like for paint color and general appearance.
I started out commuting with an Italian racing frame (De Bernardi) that I had built up with parts from another bike. I bought the frame because it was a perfect fit for me and it looked great. After 2 years of commuting on that bike, I decided that I needed a more practical bike for commuting -- that is, one that could handle a rack, larger tires and fenders. I then ordered a Bob Jackson touring bike direct from England, and one of its selling points was that they would paint it any color and decals of my choice. The BJ made a great commuter, nice looking but also very practical with mounts for fenders and racks and room for larger tires.
However, I found that I didn't enjoy riding the BJ as much as my sportier and lighter bikes, so I have continued commuting on other bikes when weather permitted. In nice weather, I often commuted on a Merckx Corsa 01 until I sold it fund another bike purchase. I also have a slight affliction of "n+1" disease and periodically pick up different bikes or frames that I find for good prices. One of those was a Ritchey cross bike that is great for off-road riding as well as commuting. Another was a Waterford sport tourer that has become my favorite bike for long rides, supported tours and recreational rides. I commute on it quite often, weather permitting, because I like riding it so much.
I also picked up another touring bike, a Soma Saga, last year to use as my dedicated bike for loaded touring, greenway rides and occasional commuting. Through it all, the Bob Jackson remains as my most regular commuting bike, however.