I just had a matronly lounge dragon at the BA Lounge in O'Hare try to deny me access by telling me point blank "We only accept Aer Lingus Gold", not even a hello. First of all madam, Aer Lingus haven't had gold in what, 3 years now? Also, I was directed to come here by the check-in staff, I'm hardly the first you've encountered.
EDIT: For what it's worth, the voracity of her protection of the sacred lounge space was entirely unwarranted, it's abysmal, stale cookies, no windows, and two types of sandwiches that look like they've been teased apart one by one by weary travellers. I've been spoiled by AA's Flagship lounge in T3.