A quick note on my commute. It is a 5 part ordeal.
Home to park and ride - Ditch bike and gear in locker
Bus to Work
Work to school - 1 mile walk
School to P&R - Catch a ride with classmate
P&R - Home

That means dragging around: laptop w/sleeve, 2 800 page hardcover books, shoes, shirt, rainpants, jacket, and food daily. You can fit some books and a laptop in most bags but the clothes and shoes put it over the top. Panniers don't work because of the walk to school. Leaving stuff at work doesn't work because of the walk to school and leaving directly from there.

Yes there are some thing I can do to make it slightly easier but they are not worth it to me.