I'm getting the hang of it, and having a blast at the same time. As you can see, I don't even need the store to bag the groceries -- I just take the store's basket out to my bike and load up the panniers. I can fit about one hand-held store basket's worth of stuff on the bike per trip. While this won't eliminate the need to drive occasionally for big stuff, it should allow me to do about 85-90% of my marketing by bike.
It just feels good!