[ROBINDESBOIS]

In Spain, we use it in at least two contexts:
Hombre, has venido ! To express surprise, you didn´t expect that person to turn up
Hombre, por supuesto que sí iré a la boda. To show reaffirmation.
And I guess you can use it in more contexts, but it´s like an intejection, and not at all rude! It´s fine. A bit colloquial I would say.

To express disagreement or exasperation we use the word Tío, not the equivalent to uncle, the other one.
Example:
Jo tío que has echo con mi coche. ( If sb hit it or damage it )
Esta tía siempre llega tarde.
Dejame en paz, tío.
I don´t know if the equivalent is guy in ENglish.