No real new info here- most people have already offered every possible opinion, but to agree with some...
Make sure you get a bike youenjoy, it makes commuting more fun. I had a similar issue, i was looking to buy a bike (one bike) to do everything. I didn't have enough $$ for more than one. I wanted a racing bike with drop bars b/c I wanted to go for fitness rides on the weekends, but still have a fun commute. I heard the same thing about racing bikes- no good for commuting. It was suggested I get a cyclocross bike, which offers the best of both worlds. Sturdy, able to attach rack, fast, sleek. Brand new, they cost a lot more than I had, but after some patient searching I picked up a great bike on craigslist for $400. I haven't looked back since. It's a blast whenever I ride. Good luck, have fun.