The main one I know of is (I may not explain it exactly right here); there is a screen that falls off the crankcase breather and ruins the engine (gets sucked into the engine and winds up in the cam or the crank) usually around 60-90K miles - happened to my Son’s colorado at about 70K. At the time, there was tons of info on the web about that, can’t seem to find it now.
Supposedly this issue is fixed now...
prematurely worn valve seats:
http://repairpal.com/worn-valve-seats-may-cause-engine-misfire-115
The passlock system has caused a fair number of issues, but that’s not directly engine related...
I don’t trust government motors - didn’t trust them before, don’t trust them now.
I run Mobil 1 synthetic and change oil and filter at 5,000-6,000 miles. I could probably push this to 10,000 or more but taking the truck to the dealer's allows a knowledgeable look over by a mechanic better trained than I am.
If there is anything to criticize, it's the lousy mileage. It's a 4WD, extended cab.