I'd be hugely disappointed to have a boy. One of the reasons I've decided not to have any children. I dislike the things boys are stereotypically interested in - vehicles, football, fighting, farts, superheros, dinosaurs, guns, their genitaliia, monsters, rough-and-tumble etc (and yes, of course I know that not all boys are like that and it's perfectly possible to have a daughter who is, but statistically speaking it's far more likely with a boy, and if I had a boy who wasn't into all that stuff I'd be worrying he was so different from his peers he'd be ostracised!)
In my experience boys have a completely different style of play than girls. Set up a small world zoo and a girl will have little families walking around looking at the animals, buying an ice-cream at the cafe, a zookeeper giving a talk... A boy will have the lions driving the zoo jeep (which can also fly, maybe occasionally squashing the little people flat!?) I just can't relate to that. It annoys me.
Boys grow into men and I, for the most part, don't like men. Aggressive, sex- crazed, selfish, intimidating, misogynistic, all that fun stuff. It's depressing to think you can plough your life into trying to ensure your son turns out right and then he goes and grooms a bloody 15 year old when he's in his mid 30s (one of my school mates, a former 'head boy', popular lad and pillar of the community did just this). I'd hate to have a son.