yes! i just have a milk-crate, but it makes all the difference.
yes also to OP on the "bicycling to work wakes me up super well" - i did in a northern US city for 6 years, and the icy/cold months when i had to rely on transit instead were remarkably more challenging, especially the mornings, even if i kept up other indoor exercise.
Then a couple of years ago I went on a bike tour, so I upgraded my bike and got some actual panniers to store stuff.
The change was amazing! Not only can you carry more, but you also avoid the strain and sweatiness of having a backpack.