I guess I've been lucky, I can't remember anything that was particularly bad. But then again I've never eaten at a lot of the places mentioned ... San Ángel Inn, ABC Commissary, Yakitori House, 1900 Park Fare. And I thought the POFQ food court left a lot to be desired, but the quality of the food we got was always excellent (from our limited choices, no substitutions allowed, if you're vegetarian too bad, with breakfast you get bacon or nothing).
The one thing I would definitely not get again is a frozen raspberry lemonade from the cart outside The Land. I thought it would taste like the Minute-Maid frozen raspberry lemonade you can get in some places, but instead if was an icee like you'd get at 7-11.
We wouldn't go back to Sci-Fi for the food (although we would for the experience), but the food was perfectly fine, just not outstanding ... reasonable quality but boring. We had excellent food at Kouzzina.