Hi and welcome!
I am training for a century too (Aug 25) and commute by bike. I find that it is a great way to get a lot of mileage in and it takes away all of the stress and hassle of driving to work. As soon as I leave the office I am on a bike ride, and granted I'm on a heavier bike, carrying stuff, but that only makes you stronger. I commute 10 miles each way, some days I'll keep it quick and other days I take a longer route. It's also really easy for me to just throw down my stuff and get on my road bike for a ride when I get home; I'm already dressed and warmed up. Longer morning rides are great too if you have showers at work because the mornings are cooler and I really like that this time of year!
The only problem that I really have with it is finding the time to take rest days. I like to get in longer rides on Sat & Sun, so I generally try to work from home one day a week or take the bus all but a couple of miles a day. The best part of commuting by bike to me is that I have so much energy during the day.
Good luck, bike commuting is fun!
Anne