First post for me on this site. I'm a Silverado/Sierra shopper, not an owner, and just wanted to weigh in on why this topic has been helpful to me.
I currently have a midsize 4X4 truck that I have used to tow a small camper (3500 lbs.) all over the US and back in October 2014 I got the new truck bug thinking that a full size would provide a more capable tow vehicle. After looking online at specs and models for GM, RAM, and Ford half tons, without excluding any of them, I decided to focus first on the GM twins. I certainly liked the looks the best, but also the tow ratings and especially, for my uses, the payload capacity stood out. At that point GM was offering some very nice deals on the 14's and after shopping within 100 miles of home I located a Double Cab 4X4 Z71 5.3 V8 with the 3.42 rear end that was exactly what I wanted except for the color. In the end I took a pass on the purchase,deciding that I couldn't live with the color for the (hopefully) long time I would have the truck.
I'm really not in any hurry to replace my current ride and when I ended up not being able to find any other 14's equipped the way i wanted, including some searches for RAM and Ford, I just hit the pause button and decided to wait on the 2015's to roll in. In the meantime, however, I found this site/thread and have been following it closely since November. I also began stopping new (2014+) Silverado/Sierra owners at random to ask about their experience and satisfaction with their trucks; so far, after talking to fifteen or so owners, including asking about how smooth the ride is on different surfaces, no one has had anything negative to say about that or any other problem.
This is certainly a limited and unscientific survey which has no bearing on whether or not anyone else has had a shaking, vibration, or any other problem. My last GM product (from several years back) which was to be my dream factory order vehicle had a driveline issue that required multiple major surgeries to the drive shaft, transfer case, and transmission before it was corrected. Even though the dealer and GM were committed to getting it right it was miserable year-long experience that I never want to repeat and left me hating the truck. I say all this simply to make the point that even if the number of folks having these issues with the new GM trucks is small, unless you've been in the situation of paying a lot of coin only to suffer through having a brand new vehicle undergo multiple major part replacement to (maybe) make it right you really can't understand what a bad experience it is - I feel for those folks.
On the other hand, based on data recently reported by pickuptrucks.com on January 26th, GM sold a lot of half-tons in 2014, more than any other manufacturer. Considering this, again not to minimize the real problems some folks have had, it appears that the absolute number of significant problems is probably small.
This forum has helped me in several ways and I'll probably be watching/shopping for several more months before deciding which new truck to get. On the positive side it's been good to hear how many have had the shaking/vibration corrected with better tires or, if something more significant was needed, that the dealer was willing to do what it took to fix the truck to the owner's satisfaction. On the negative side it really pisses me off to hear about dealers in denial or those that just want to blow the customer off - a really good company shouldn't be allowing that to happen, period. I've been through the lemon law process once in my many years of vehicle ownership (although it was an easy process with a manufacturer that wanted to make it right) and wouldn't be hesitant to do it again if needed. It's not fun and takes time but with persistence it does work.
Finally, for those like me who are following the forum to learn something useful I think we want to hear the details from owners that have problems that get fixed as well as those owners that have problems that don't get fixed and have to go another route like a buy back or trade for another truck, even a different brand. The good and bad outcome stories - those are the posts I like to see. The sniping may be entertaining but it's not very helpful.