While I was doing my reading for Wyrdsmiths yesterday, I tripped over a character saying "Ack, this paper is ripping." (paraphrased)
The interjection "Ack" just bounced me. I don't know anyone who says "Ack," though I recognize that it is a commonly used espression of grumble or difficulty. Similarly, "Argh", "Urg", "Er", "Uh", "Ah", etc., some of which bounce me more than others.
The things is, I can see the reason for the writer to want to have a tool like this at his/her disposal. This is closer to onomatopoeia for the expressive grunts that we make than anything else (though I know some would argue that point), and I don't think the abstraction of "He sighed/grunted/growled" is quite as effective. I can see a distinction between I lifted the rock, grunting and "Ungh, this thing is freaking heavy!"
But if I'm getting bounced from the story because of it, then either A)it is not being used effectively, B)it isn't the right choice of onomatopoeic interjective expression, or C)it is one with which I am unfamiliar enough to make me stop and think "How exactly would that be said? And why would they say 'Urg' instead of 'Uuh' or 'Eew'?"
How do these expresions function for you, as a writer or as a reader? Why do we persist in using them? What do they bring to the table, as a tool, that overweighs the possibility of bouncing a reader--however momentarily? And if you don't use them, why not and what do you do instead?