I take that flight all the time (I'm on it next week.) It's usually a pleasant flight.
Really, the mid-con food is so mediocre, that it's just not worth it. That sounds cynical. If United served better food up front, I'd feel differently. But they don't. Maybe one day.
I don't have a favorite take-out place in Houston. I'll have to think about it for this trip.
I get more annoyed about missing meals on westbound transcons. The flights are a lot longer, and the food is very slightly better (at least there is ice cream.) So that's the only time I pay attention.
In this case, I'll get lunch or dinner from Mexico City to Houston, so I might just grab something to take with me for the Houston-Seattle flight.