Interesting topic.
I don't like a backpack because I don't like to carry the weight on my back. It reminds me of hicking not biking.
However, my current setup needs some tweaking. I have a rack and a rack bag, but it was the small rack bag and is barely big enough. The problem I have is I need more clothes for the am commute than the pm commute. It looks ugly and apt to come loose. I am thinging of getting a saddle bag, but haven't decided yet.
I will be curious to see how others solved this problem.
Huff