I carried concealed in a shoulder holster for a while, before I knew about OC. Since I have been OC'ing, I have only worn a belt holster. The shoulder holster I had was a cheaper one, and it ended up being uncomfortable. I am looking forward to getting a quality shoulder rig so I can OC/CC with it. I liked having the weight off my hips, and in a lot of situations, it just felt more natural to wear the shoulder rig. As far as reactions from the sheeple, I don't know, I haven't OC'd one. You should try the holster on with your gun in it, and if possible, with 2 mags so you can feel the weight. Wear just a light t-shirt and see if any of the clips or adjustment tabs catch under your arms or anything like that.
I definitely realized that with a shoulder holster, it HAS to be comfortable to wear or it will drive you nuts.