Back when I was flying, I tried to be more personable with the customers. I thought it was good to try and make them feel relaxed and "at home" of sorts. Looking back, I dunno, I can't say it was the best course of action. Because when the S hit the fan, they needed someone there to take charge and order. Hard to take a Captain seriously in an emergency when they were just playing a harmonica.
Now as a police officer, I'm always Officer Sxxxxx. No first names, EVER. I don't even write my first name on tickets, reports, etc. Always just my last name. Even fellow officers call me by my last name. It's about respect, professionalism, and authority. My wife, parents, and some friends call me by my first name. No stranger I just met.
If I were to jump back into the cockpit, I'd definitely always introduce myself as Captain Sxxxxx or F/O Sxxxxx. Not because of ego, but because of authority and respect. Some will scoff at the idea of it. But if you want respect for the profession, you're going to have to demand it by your actions and demeanor.