I test drive the Colorado Midnight Edition with the V6, a Z71 with the Duramax and a Silverado 1500 with the 6.2L.
The Midnight Edition seemed to toss us around a bit on bumpy roads, and in a different way than my wife's JK Wrangler. Only thing different vs the regular Z71 was the Duratrac tires. It was quite a bit less stable under heavy braking than the regular Z71. The V6 felt more powerful than I expected, and if I didn't put 70+ miles a day on my vehicle I may have gone for that.
The Z71 Duramax drove like a truck. It sounded like a truck - has a little of that diesel clatter but it goes away when under light load, which I kinda like. Even when not in tow mode, there's enough engine braking that it held speed downhill whereas with the V6 I had to brake going downhill to keep from going 5-10 mph faster than I intended. It felt very stable compared to the Midnight Edition.
The 1500 with 6.2L was interesting. The bigger size was most definitely noticeable and there was no mistaking that it was faster. Hit 80 getting on the highway in no time. It had the same feel as the V6 Colorado - tossed us around more than the Duramax Colorado. It would definitely be a fun truck to drive but I can't justify spending an extra $15k right out the gate and getting 30% less fuel mileage for some extra fun when accelerating, extra towing capacity that I likely won't use, and some extra space that I don't really need. And while there's no doubt it's faster, it's not so much faster that it made me say, "I gotta have that." I know it's a 3 ton truck... but I guess I had high expectations.
I asked the salesman to hold the Duramax for me overnight to think about it and talk to my wife about it a little more, but I think we've already decided to get back in touch with them in the morning and tell them we'll take it. The only things missing that I would have added if I were building it on chevrolet.com is the spray-in bed liner and the block heater.
I don't really need the block heater... it might be convenient 5 days out of the year, but I think I can squeeze it into the garage if I really think I need to on those -10 degree days. As for the bed liner, I might try a roll-on if I feel like doing all the prep... or I may just get a bed rug for those days when I want to haul some landscaping stuff. For the most part, I think some of the rougher things I haul, I'll use a trailer anyway.