Goodings is more expensive than most grocery stores and has a smaller selection of items, but it's very convenient. We always drive and bring our own breakfast (cereal, granola bars, pop tarts, bagels, etc.) and a few snack foods to keep in the room. We usually have room in the car for all of the non-perishable items that we take with us so we just need to stop for milk, cream cheese, and maybe yogurt. For us, Goodings is fine for that -- simply because of the convenience. When we went to Disney in June, we didn't even stop at Goodings, we just picked up 1/2 gallons of milk ($2.99...probably the same price as Goodings) and cream cheese (no charge on the days we got them) at Landscape of Flavors at AoA.
That being said, if you need to pick up all of your food, you are definitely better off stopping at a Walmart or Publix in the area. We have bought everything we needed at Goodings on one or two occasions when I didn't have room in the car for everything. It just wasn't worth it to us to take the time to drive out of our way to save $10 on the 10 or 12 things we needed -- we've never spent more than about $70 there for breakfast and snack foods. But I understand that we all have different priorities and budgets on our trips so we all do what works best for us.