Y'all doesn't have much place in the written language, but it wasn't until I moved to Texas a long time ago that I realized what a useful word it is in conversation.
In business, I use it to refer to "your corporation" without sounding like I have something stiff stuck somewhere painful.
Y'all is word that is badly in need of use in America as Engish has no word for "all of you." However, it is my understanding that the Southern work "y'all" is meant to apply to a single person "y'all" rather than to "y'all" as a group.