To clarify- my commuter bike is a Kona Jake with a rack. Back in my single days I had some buckets for shoping, but now with a baby if I take the bike shopping I hook up the Burley trailer because that way I can take the baby off my wifes hands for awhile and 2) my wife and I have 4 kids at home so "going to the store" generally involves coming home with 35-40 lbs of groceries.. . and a 25lb toddler. Fortunately the store is a mile away. The panniers would be mostly for the next few months... I can justify them on the gas I would be saving using the bike- but as I plan on biking panniers or no I cannot say they will "save" me money without some serious boy-math.

Thanks for the opinions though- I may take a trip to a bike shop and take a look this weekend.