Well, the qualifying criteria from the OP are kind of all over the place, so that being said:

My bane right now is LGA. This is mostly based on physical plant of the terminal, which is an abomination. Fortunately the RCC remains comfortable. UA staff at this location are top notch, at least to this GS. Robert at the check in desk and Dennis in the RCC take amazing care of me.

As far as very enjoyable terminals, it's just a small UX station, but I was really struck by how nice a job they did in MSN - granite countertops at the check in desks, limited by decent food options and an overall comfortable airport considering lack of RCC, etc.