I've never set foot in a GM, but remember seeing great deals, online.
I've bought many guns over the years and sold some. My favorite transactions are in-person for vintage hand guns that fly under most folks' radar. I particularly enjoy "talking" guns with other similarly interested gun guys and I appreciate learning from them, too. (I imagine the OP was one such person.) I actively read a lot about older production firearms, as probably most of us here do. Since I am an informed buyer, that has served me well at the "used gun" counter.
Great thread, OP! I've enjoyed reading everyone's recollections.
I wish I could have visited your store.
-Bill