Yeah, I agree that there's no reason not to use your carbon bike for commuting. I've always thought it was absurd that people would suggest with a straight face that you not ride your most comfortable and enjoyable bike for 80% of your riding, and instead get a beater.

As other people have said, main concerns are -
1. Someone stealing your bike off the front of the bus
2. If your components are expensive, they'll wear out because you're using them more - just a question of if it's worth the cost to you

Another option, if you own a car, is to drive part way, find a good spot to park your car (like a parking lot in a decent neighborhood), and do things that way rather than taking the bus. Biggest problem is just making sure someone doesn't take your bike off the front of the bus and walk off with it.