I have a Glock jacket that my wife got me for Christmas a couple years ago. I wear that sometimes when I feel like advertising my 2nd Amendment rights. Every now and then I get in this... mood, I guess you could say. I get a little fed up with all the gun-fearing wussies and anti-gunners and throw on my Glock jacket. Not long after I got it, I walked into a gas station (carrying my Glock underneath, of course), and a police officer was hanging out talking to the clerk. As I was paying for my stuff, he asked me about my jacket. We had a great conversation about Glocks and guns in general. He was carrying a Glock 22, and said he really liked the reliability and accuracy, but liked his personal Sig better. Never did ask me if I was carrying.
Other than that officer, I haven't had any other comments about the jacket.