I don't care for that word cos it sounds weird in my mouth... I have a few English words I feel that way about. It does not bother me when others use it though.
It depends on the situation. In a professional setting, don't use it. To make a point when in a more relaxed atmosphere, go for it. Say someone does something inappropriate, then saying "That ain't right." would be acceptable. Especially if you say it with a southern drawl. And I am from the south.
It's use was endemic in 18th century dialects, both British and North American (though you can see how one would follow the other). Nowt wrong with it. I use it as a reiteration, like f***. It adds texture.