Besides the transmissions on the 8 speeds non-diesels I can't really think of anything major. There are a number of people who have had a number of issues, but they are seemingly both small in quantity and importance. The ones I can think of off the top of my head:
Low coolant causes gurgling in the dash.
Some seepage out of the front of the rear differential that discolors the metal but seemingly doesn't do anything else.
Some heater cores started leaking prematurely, so prematurely it was well within warranty.
My issues are more design issues, like the headlight and 4x4 switch being identical, right next to each other and out of sight (ditto the trailer brake controller being out of sight). The manual operation of the automatic transmission is bizarre to those not used to GM products. So many controls seem backwards that I'm surprised you don't lift the turn signal lever up to turn left. And finally, the incandescent headlights are pretty pathetic, but I don't care because I live in an urban area--the high beams are adequate.
So nothing major. And overall it is a good design--I've been happy.
Edit: I forgot, some people aren't happy with the shift from 1st to 2nd first thing in the morning, and some people aren't happy that when you first shift into drive or reverse in the morning it can take a second or two to engage. I personally think both those are somewhat normal automatic transmission behaviors. My six speed sometimes does the former.