This is my third Denali pick up. Huge buyers remorse buying black but that's my fault. It does look amazing few hrs after its washed. Was really wanting the 6.0 and eight speed tranny but they're so hard to come by I had to settle for the 5.3 and the six speed. My 07 had alot more power it seems. Plus it was all wheel drive. But I am getting around 16 miles per gallon instead of 13.5 with my old Denali. Still working through the countless menus on the electronics. I'm over my trial for the Wi-Fi and was not impressed.The drivetrain has a vibration at around 41 miles an hour that I need to take back to the dealer and have checked out. It was an insane amount of money but I'm not unhappy.
UPDATED from 10/2015 I have owned this truck for 15 months- mileage now at 23,452. GPS roof antenna unit shorted out within a week after purchase or was likely not working when I purchased the truck. I believe it had a defective seal on the roof. Replaced by dealer. Nice looking truck. Decent fuel mileage. The truck says I am averaging over lifetime18.6mpg, it has about 23,452k miles so far. My truck has the 5.3L w/6 speed transmission/ 3.42 rear axle ratio. I opted for this engine configuration thinking it may get better mileage than the 6.2L/8 speed trans. The truck handles much like a Corvette on sharp turns at higher speeds. Not crazy about the ride; however its ride is MUCH better when carrying a heavy object in the bed or towing my utility trailer with a heavy zero turn mower loaded. I have the 4x4 Denali model which has the magnetic shocks. I drove another new GMC truck with the V-6 engine while my Denali truck was getting the GPS antenna roof unit replaced which took over a week to obtain the parts needed. I really liked the lower priced V-6 truck, although the interior creature comforts was NO comparison to my completely creature comfort-loaded Denali model, which was the reason I bought it (and the front grill). Both trucks are quiet riding. Horrible price tag. No complaints so far after 15 months (2 recalls and the info center needed updating).
Went to the dealer thinking new Suburban I ended up with a Sierra Denali! Briefly stated, I have had Suburbans for 20+ years to haul materials for my business and personal use i.e. hauling black labs, gear for various outdoor adventures, etc. I actually have actually used a Suburban for what the vehicle was initially intended! Unfortunately, the new recently redesigned Suburban is an engineering disaster for folks like me. The rear storage area is much smaller and chopped up. Also, if you have to crawl in the back you darn near need a ladder to get in. It's clear that GM has targeting soccer moms for the new Suburban. It's strictly a people hauler...period. So, I just happened to look at a Sierra Denali crew cab pickup. After a test drive, I was ready to buy. The back seat area is roomier than a Suburban and will seat 5 comfortably. I could go on and on, but the bottom line is I love this vehicle. Best of all, it cost far less than a comparably equipped Suburban!
I use my '15 GMC SLT 4X4 for highway trips to Rochester, Minnesota, in the winter more than anything else. It drives and rides very good. Power is pretty good, and gas mileage is better than average for a full sized half ton truck. The high hood limits close up visibility for parking. The most important thing is....my wife likes it (if Mama's happy, everybody's happy). My only complaints are...1) - the shifting of the transmission is a little mushy, and 2) - the high beams are not bright enough.
Ive owned this truck for only 3 months now, and have only put 4300 miles on it. Fuel economy is great, but I cant stand to be driving in it because of so many interior rattles. If somebody on a harley pulls up next to me, or any other vehicle with an aftermarket exhaust it starts with a very high pitched rattle under the dash. If i HIT EVEN THE SLIGHTEST BUMP IN THE ROAD, IT SOUNDS LIKE EVERY SCREW IN THE CAB IS LOOSE. I drive professionally for a living, and refuse to own a rattle bucket for my hour commute home. Wish I would have just kept my 2012 tundra.