I've heard "Mr. + first name" used as a rather disguised way of displaying a patronizing (or condescending) attitude towards the person addressed in that manner. Maybe it's just a local thing, or maybe it's just me. Anyway, that's how I've heard it.
It would depend on who it comes from, how it said and where it is said. In any event, I prefer to not use or hear the "Mr." title, generally speaking. There may be exceptions once in a great while.