I'm just outta college and usually get a double look on SC check-in -- but as I proceed as if I belong, I always get decent service.
I get way more dirty looks from all the old people in the skyclub as if anyone under 40 shouldn't be allowed in this sacred place.
I'm always carded by the bartenders but they are always very professional and polite. After all they can lose their job if they don't card the wrong person.