I cannot wait for this to launch in San Francisco.
Depending on your location in the city, grocery shopping without a car can be a pain if you're buying enough food/organic produce/grass-fed meat for 21 meals/week x 2 people.
Add the cost of ~1.0-1.5 hours of a ZipCar on top of the 'organic premium' and a delivery service makes sense.
In NYC, FreshDirect was worth the delivery cost. They charged per delivery rather than a subscription. Their food quality, variety, consistency, time-savings, and organic options always exceeded my expectations and made it worthwhile.
I'll pay the fee on top of my Prime membership for this in San Francisco.