I OC around Pittsburgh and Allegheny county every day and for the most part, no one ever says anything.
Once in a while, I'll get a "hey, is that legal?" or the like, but those are just opportunities to hand out PA Patriot's flier and educate a little bit.
I have had one very bad negative encounter - fortunately there were no repercussions from it.
Aside from that, the worst that's ever happened is a "please cover" request once or twice.
You can read my experiences here:
http://www.pafoa.org/forum/concealed...-area-o-c.html
And my BEST encounter ever, here:
http://www.pafoa.org/forum/concealed...start-way.html
My WORST encounter ever here:
http://www.pafoa.org/forum/concealed...aurant-oc.html
And the FUNNIEST here:
http://www.pafoa.org/forum/concealed...xperience.html