I'm going to advocate something different, and it's not for everyone, but if there's a store near you that you can try a couple out, don't overlook recumbents, especially for commuting. For me, the comfort and ease of riding is totally worth it for day to day commuting. I still have a DF mtn bike for non-commuting, mostly offroad leisure riding, but I actually look forward to my rides a lot more now (of course, I'm getting older....).