06 Duramax bone stock with 130K, I've owned her since 25K and a little over a year old. Overall, great truck as others have said. I've probably had more than the average # of issue but nothing too serious.
Leaky tranny lines
Xfer case (surprisingly not pump rub but still a replacement)
Both front hubs
pitman arm and some other various front suspension parts - total of 3K spent at the dealership in the past 2 years (my truck is a company write-off and I NEED it fixed ASAP when something goes wrong otherwise I'd never pay so much for repairs)
Parking brake cable snapped once
The thing goes through bulbs of any/all type with blinding speed
Power lumbar in the driver's seat broke a few years ago an I haven't fixed it
Still on the original brakes and had 50%+ at all 4 wheels at last check (are these things made of concrete? I've never seen brakes wear like this - they are very powerful as well)
There may be a few other things that I'm forgetting but that's the main list. Like I said, it seems like more than average from what I can gather from reading around the net.
Overall, I love this truck and don't have the $50K to lay out for a new one so this is it for me for now. As far as price, at 130K 4X4 LT CC SB I'd like to think I could still get 20K pretty quickly. Mainly, due to the demand. In more normal terms this truck should worth closer to 15K.
Also, as for chipping I don't think you can tell for sure on the 06/07. I'd call a dealer to see what they say. Mainly, I'd be looking for gauges or holes where they were once mounted..... or lift kits or other aftermarket stuff. And you're very wise to be looking for chips. 75%+ of the trucks I see with big problems have chips.