I judge my ratings on places like these by the speed, frustration factor or lack there-of, cleanliness, and competence of the employees.
I usually go to Sonic for Iced Tea or Diet Coke.
They get my orders right, and are always friendly. They have a few REALLY good employees here as well, in terms of customer service!
The place appears to be clean- parking lot is picked up, and I haven't noticed anything gross here that makes me want to leave.
An interesting note- a lot of people eat here AT the Sonic, at the tables. I think this is representative of the neighborhood and a relatively young crowd. It's a positive thing to see that people will stay to eat and visit, not just drive thru.
Sometimes this location can be slow for unknown reasons- maybe the waiter on skates is cooking in the back? If I see a line, it makes me nervous and I don't stop.