DNF's - Do You Finish Every Book, or Are Some DNF's?

I admit it; I've never read a book I didn't finish. No matter how bad, how horribly written or plotted, I've finished every single book I've ever cracked open. Whether it's the hope that it WILL eventually get better, or that I just have to know how it ends even if I hate it, I feel this intense need to see the story to the end.

Once, just once, there was a book that almost became a DNF for me. It wasn't a romance at all. It was Without Remorse by Tom Clancy. A really awesome story - bogged down in tons of technical jargon that had me going back pages to see if I could remember what weapon did what and who was on the good side. I put that book down many times over a year - but always came back to it. Again, the central plot and characters are fantastic; I just couldn't keep track of all the details. I eventually finished that book - and have kept a copy on my shelf ever since almost like a trophy of the accomplishment.

Why am I bringing this up? Because I just might have my very first DNF. Although it's an audio book and not print, I don't think I would be interested in the story anymore. It's literally the worst audio book I've ever heard. The voices are horrible imitations of Hillbilly cartoons. The Hero's voice is by far the worst and he even says Ga-Ron-Tea (guarantee) in a voice straight from Yosemite Sam at one point.

This audio book is so bad I literally cringed driving down the road when the hero speaks or a new character with some insane fake southern accent is introduced. The author is a very well know one, and I've heard people love the books - but I do not think I could read these in print without having those voices playing in my head.

I won't go into details about the book here since I might still plan on reviewing the audio book. I can't stand thinking there might be a book out there I didn't give enough of a chance. There's a part of me that would feel guilty for not reading on when an author put so much into this. Why do a feel this way, and an even better question is do you ever feel this way?

Do you finish all the books you pick up, or do you have no problem putting down a book you aren't enjoying? Has one certain book let you down, or are you a frequent DNF'er?

I want to know - am I the only one who finishes them all? Should I stick it out on this audio book so at least I can honestly say if the story was good or not?