I have a new 07 G35 Sport on order and have been debating (while I impatiently wait for it's arrival) in my head about how to handle the front... I've decided that at the cost of a clear bra, $600-$800, and the fact that they are visible and take away from the cars appearance slightly, and they only protect against most tiny rocks and debris while offering zero protection against anything you can pickup with your fingers, plus the removal process and expense when you want to take it off.
I think I'd rather go without it and take my chances, for all the negitives and costs, I'd rather just have the front repainted, and if it's really just a small amount of nick's and minor chips, you could just have it detailed to "good enough for a 6 year old car". if it takes a big enough hit, the bra wasn't going to help you out anyway.
as P1et stated, and I'd probably go even further, 95% of it is keeping your distance, not just from trucks, as in the long run, the cars do considerably more damage then trucks because you probably drive behind hundreds of cars a week, vs the handful of trucks doing 50+ mph in the same week.