The brakes on my '08 feel and stop better than my '02 so I'm not bothered by the rear drums. Would I rather have 4 wheel disc? Sure, for aesthetic purposes. Are 4 wheel discs worth spending more money for? Nope, not for my needs. I don't feel the rotors on these new trucks are as good of quality as they were on the 800's. The rotor's on the '07 I had started warping (vibrating) just before I sold it at 12,000 miles and I've already had my front rotors turned on the '08 at around 6,500 miles. I rarely pull a trailer and never haul anything heavy.
I do agree that the rotors (front and rear) on the GMT900's are cheap (Chinese crap). I haven't had any warping issues yet, but my right front rotor has some grooves in it already, but they have smoothed out and do not appear to be getting worse, so it may have been from material transfer when they were new. I plan on upgrading to some nicer rotors when these wear out. But upgrading to higher grade rotors is alot easier/cheaper when you don't have to convert drums to discs.