Normally I would say GMC or Chevy (brand preference) but I was considering a 2015 and started to do some research.
Apparently a significant number of 2014s (15s as well?) have a real vibration problem at hwy speeds. Also, for some of these the issue is apparently unfixable with dealers changing tires, shocks, driveshafts, rear-ends and motor mounts.
Google Silverado/Sierra vibration and you'll find several videos documenting the problem and several threads (one is over 280 pages) documenting problems and problems in getting GM to fix it.
To add to that, I'm hearing complaints that the 5.3 with it's switching between V4 and V8 to be annoying and that the transmission/engine match results in a sluggish and delayed throttle response.
Finally, there have been a crapload of small recalls for the 2014s
Overall, I'm highly disappointed because I really like the new Silverado but I'll be shopping for a 2012/2013 to avoid these new problems.
CAVEAT: As with any Internet auto problem it is impossible to know how common the problems are and obviously many buyers experience none of these problems. However, there seems to be enough smoke around the vibration problem to send me in another direction.