I started commuting about when I started riding a bike (in my adult life, training for triathlons). In my old job, we had showers and lockers, so I didn't have to carry much stuff. This was about a 25-30 mile round trip and my bike was parked at a bike rack in our Dallas suburb company parking garage. I started out using an old Schwinn I bought from a coworker. After I realized this was for me, I upgraded it with Supergo Korso wheels and 8-speed bar-end shifters and rode it from late '05 to mid '06 (note I'm a Mar-Oct commuter):
Then, I got a deal ($375) I couldn't refuse on a tri bike and the Schwinn sat and I pretty much always rode this starting mid '06:
Well, since the Schwinn just sat and I loved that old bike, I converted it to a fixed gear and split the commutes between it and the Klein. I also switched jobs lengthening my commute to 35-40 miles round trip. I have no showers or lockers, so I installed a rack on the Schwinn and still split the commute between bikes using a backpack on the Klein. I also store my bike in our company's closet (small company).
Now, I've got a screaming deal on a new Javelin with Campy Veloce and have sold the Klein (sniff, sniff), so my commutes are split between it and the Schwinn: