Okay, I've gotta throw this out there. If you're buying the bike solely to do the flat commute that you described, a single-speed makes a lot of sense. Less complexity, less maintenance and all that. You want to ride with racks, fenders and fattish tires. One really nice single-speed comes right to mind that would fit the bill perfectly. The same one that I use for my commute interestingly enough. The Rivendell Quickbeam. I'm biased because I really love the bike but it would be an excellent choice for your commute.