Well a couple of days ago, a shoe salesperson at Brooks Brothers changed my life. I know that seems dramatic but having shoes that fit really make a difference if you're walking around all day. I asked her to get me an 8/8.5E Edward Green. She took one look at my feet and refused. I was stunned. She pulled out the shoe sizer and showed me.
I am, in fact, a 7.5 wide! Though the 7.5/8E EG's fit pretty well on me, I actually could feel arch support in my dress shoes, which I had never experienced before.
I was still skeptical, so I went to Leffot and asked them. Sure enough, they confirmed that I'm somewhere around 7.5 E/EE, though occasionally 8 standard width would be ok in some shoes.
Walking in the shorter shoes with more width gave me better arch support and better balance while walking. It really is night and day.
I guess my main point is don't assume you know what size you are based on what you've always worn. It's worth taking a little time to really figure it out before you shell out that cash for Lobbs or Edward Greens or any shoe for that matter.