I'm the original owner of my 4wd ext. cab ZR2 with 100K mi as of 12/05, and the truck has been a blast to drive off road and to haul stuff with. However, there have been several major repairs that have cost much $$: Tranny at 50K mi, fuel pump, pwr window motor & switches, 6 batteries, oil leaks, two A/C units, two alternators, electrical problems, idler pulley and recently some ignition system problems. Also, at 16 MPG on the highway it is a lousy commuter. I'm convinced the ABS never worked right in spite of at least 3 recalls/bulletins. The 4.3L Vortec V6 has been strong and burns no oil.
Interior is very comfortable. Simple things like visor extensions and clean instrument and environmental control layout go a long way. It can be rear-ended quite hard and suffer minimal damage. Mine's been hit four times.
Reliability of major drivetrain components and accessories. Bigger gas tank (at 16 MPG, I avoid going more than 200 mi with the 13.8 gal. tank).