Long waits. You'll get your food faster at many other non-'fast food' restaurants. The 'drive-thru' line quickly fills up and begins to block the flow of traffic in the parking lot. It's not uncommon to be not given requested sauces (e.g. hot sause for sausage burritos, ketchup for fries).
Same barely edible quality food that you might expect to find. Customer service is worse than the sub-par service you might expect.