Wow, what a pretty boy! Do you happen to know his registered name/pedigree? I'd like to look him up on the Pedigree Query website.
As for conformation, with these photos it's hard to tell, but he appears to be hollowing his back in the under-saddle picture, and his neck looks "upside down" - see how it has a upside-dow bow shape to it? But that's probably because of the fact that he doesn't appear to like his rider much, and he seems resistant. But, a soft-handed, quiet-seated rider and properly fitting tack would fix that.
He's got a nice, long neck otherwise, good shoulder (not too steep), and his legs look good to me. His hooves need some trimming, though, to get the toes shorter and heels back where they need to be.
He's gorgeous, though, and I don't see any flaws that couldn't be corrected with a good rider, correct training and a good farrier! Pretty horse!
P.S. What price are the owners asking? Does he have any underlying heath conditions?
"Horses are proof that God wants us to enjoy life"
SAVE THE MUSTANGS!!!!