ha. i use dude that way too, as an exclaimation. i also use it with women, but im in california, so its rather typical.

who else uses dude in a certain way when you are trying to express sincerity.

such as: "no, DUDE, seriously, that is NOT cool" lol

Ha, that's how I use dude too!  I'm always exclaiming it and drawing it out into two syllables - DOOOOEEEEEEED

I do the same thing.

Is dude really not gender neutral in most of the states?  I guess I'm behind the times as well because I use "dude" and "man" interchangeably as exclamations.  As in the examples Devin and Jimmy gave, and as in "Man, what is your problem?" and "Not cool, man, not cool." 

The US South is a bit interesting. Dude and man can be used for everybody. Many times men are called dear, sweetie, sweetheart, etc. but always by a woman- especially if the woman's older than you. If a guy calls you those names though either he sees you as a female or is trying to piss you off. Men never call each other those things.