I agree with you about disposition. I think those can be way off. The data that produced the disposition scores, mostly comes from seed-stock breeders and is a judgement call. My own observations indicate that at least some bulls that scored well for disposition, will have flighty calves while others that scored more poorly have quiet calves. In my operation I only keep replacements until they are old enough for a disposition score as yearlings. The nervous and crazy are gone, so my scores would make any bulls numbers look good, even if 10 heifers were culled in order to find the quiet one.
Weaning weight can be highly influenced by environment, and therefore I''m not terribly concerned with those numbers, other than not wanting one in the lowest percentiles. Where I find the numbers to be most accurate and helpful is with birth weights and mature height and weight. Those numbers can help you avoid animals that are too small or large for your operation. Carcass numbers are also accurate I've been told, although my calves are sold at weaning, so I would not really know. I've also been surprisingly pleased with the apparent accuracy of calving ease scores.
I'll give an example. I had a bull with a 99 pound birth weight and a 700 pound weaning weight raised on this farm. I kept him to breed to cows hoping for good weaning weights. I had another bull with a 70 pound birth weight and 650 pound weaning weight. He came from a long line of calving ease cows and bulls. He was kept to breed the heifers. I know these weaning weights aren't impressive to those living in areas with fertile soils and that supplement their cows or calves, but they are good weights for my environment. The bulls both had genomic profiles run and they indicated the bull with the 99 pound birth weight would likely sire smaller calves at birth and at weaning. I did not really believe it, but after 4 years of calves it turned out to be true. That 99 pound bull actually had an average on his offspring birth weights that was lower than many of the calving ease AI sires I used over those same years. The other 70 pound bull performed pretty much to his genomic profile also. On average, his calves were just slightly larger at birth compared to the other, but weaned an average 15 pounds heavier. That was just the opposite of my expectations when I first selected them, but the genomics were right on.