I bought a late model 07, same as the 08s... sucked... had issues with driveline alignment and it spent the first month in the shop and chevy wouldn't stand behind it -well, they fixed it but then they expected me to be happy with shims for a final fix and no extended warrenty! i FINALLY broke it in and am now getting about 13 mpg. if you go over 60 you see a big drop, but you get tha with diesel too... towing sleds on a deck. it can do it just fine and hold 80 over the passes! but it SUCKS the gas!! down to 9.... however, do the calcs and depending on how much you drive it still might be less than a diesel if you consider the up front costs of diesel, maint costs and the cost of diesel vs gas right now....
if i had it to do all over again i would prolly still go gas but i would get the standard. don't like the way their new trannismission works. if you're in tow haul coming down a hill and tap the brakes it shifts down. with the winter driving and sleds on the deck it put me in a sketchy position every now and then. don't use it any more... and the 'manual shift' is set up to protect the truck so much you can't get it to wind up or down at all... still shifts too much for my liking on snowy roads!! shifts really smoothly though -which is good except it's hard to tell when it will! will make summer time driving nice though....
i got an crew cab with a full box. it's not the smoothest ride, but it's a big truck... i prolly wouldn't go that big in the body, it's nice to have but with gas the way it is i prolly shoulda made some sacrifices and lived with out a TON of 'room'.
the finish on the truck... well, i think the idea that chevy has the nice finish is kinda old school, the other trucks have just as nice of a finish these days...
the motor... ya, it's a beast.... i thought at first it was HORRIBLE because it really sucked the gas. my brother busted me out and asked how much my foot was in it?!?! opps! it gets up and go and is fun to drive, but you pay the price! but like i said, if i could do it over again knowing the prices and the market i wouldn't go with that big of a truck.... you will have little to no resale value on it... the market is changing, bigger is just not worth it.
also, yes, some diesels can get 22 mpg but they drop when they're towing too and when they really step on it. in fact i've heard they drop faster than gas motors when you step on em! also, looking at the costs of things include the chips and performance things people are doing to most of those diesels to get that outta them....
just my thoughts. i wouldn't do the 6.0L. and after my last chevy experience i wouldn't go with them either and i had a chev with 200,000 miles on it before that that i loved. i think i got a lemon, not that all of them are lemons but i got one and chevy did a REALLY poor job of standing by it. it was a 4 month ordeal where they changed caseworkers 4 times on me and offered me less than what i had originally but with fancy wording. i didn't fall for it and busted em out. they agreed and said, well we can't offer you any more then.... sorry.... SUCKS TO BE YOU!!!! long story, ugh, i can't believe i even got started on this.... but ya.... i don't think the 6.0L is the best rig out there unless you ONLY care about being able to pass everyone while going up a hill at 80 towing a few sleds!!