I used to shop Vons online when I lived in San Diego. It was nice to be able to do my grocery shopping online, but I usually had to wait a few days before getting the groceries so it wasn't as convenient as it should have been.
Additionally, the price they quoted to me online was always significantly lower than what they'd actually charge me.
There weren't any good alternatives to me, but they aren't really running a real online supermarket. The prices they list are just "estimates" and the final bill is out of your control, they just show up with the groceries and a receipt for what you were charged.