I'm sure given the millions of GMT900s built there are plenty of good ones, but in my experience the GMT800s and later K2 trucks are generally better designed and built.
900s have lots of body issues and AFM was a joke on the 5.3s. There is a reason why most any GM dealer has at least one full set of active lifters and associated parts in stock, we even used to stock the camshafts. Granted, that doesn't apply to 4.8s, but the body issues do.
Amazingly, the black dash is still in good shape on the one at work, but it's the base dash. I've got the upper level dash in stock because they crack all the time, pretty sure I've got a base door panel too since that's the only way GM sells the interior handle that breaks all the time (there is an aftermarket handle only replacement). The rest of the interior on the truck at work is falling apart for no apparent reason (pillar trim fell off, window switches pop out, seats are junk). The driver's door also feels like it's about to fall off, though I will say I haven't encountered that on many other 900s. This truck is used for delivery, so the door is opened a lot, but it only has around 150k on it. We have 300k+ mile 800s that have held up better aside from sloppy steering. The later K2 trucks seem to be a huge improvement aside from AC issues and sometimes "Chevy shake." The engines are definitely better.
Sorry, just my experience. I don't feel the 900 was an improvement on the old trucks aside from rack & pinion steering. It was a stopgap to get a more modern truck out during hard times, but it wasn't a better truck in my experience. The K2 was the better truck they finally came up with.