I understand where you are coming from and I am beginning to see this issue as strongly part of the current gender debates which also lead to gender confusion in children and adults.
It is really not about the sex of the baby but the gender stereotypes we feel we have to follow with them.
I have two gorgeous little boys who I love more than life itself. But yes, when I found out they were boys I did 'mourn' the daughter I would never have. I still do sometimes, usually when a friend has a new baby girl or I spot a new range of beautiful girls clothes somewhere.
But in reality, my boys are people first and foremost. I cannot determine whether their personalities are due to being boys or just being children, and it really doesn't matter, because they are just fab the way they are.
Much of the problem is how rigidly defined and reinforced stereotypical images of boys and girls are these days. Your baby is born, you have to have a colour coded congratulations card and clothes to match. That's how it starts. Then later down the line you find yourself wondering whether the toys and clothes you buy them, and the activities you do with them are gender-appropriate. What nonsense we are compelled into contemplating!
My older son loves playing with pretty much any toy going. He does love cars and trains and building but he loves being creative too. Recently I had thought he was beginning to conform to stereotype as he showed more interest in role playing games than arty activities so I though, 'oh ok, I mustn't push him'. But just now he has been wanting to get his colouring things out and did me to sit and draw with him. So it was just a phase, nothing fixed in him at all. And from a developmental point of view, it will gives him a rest from using his gross motor skills to concentrate on fine motor skills for a bit.
I do sometimes long for the pretty girls clothes. I wonder if this is in part due to the more gender neutral clothes and toys I had as an 80s child and I would have quite liked those clothes for me rather than my older cousins' hand me downs.
But a frivolous anecdote to finish with. Yesterday I was in Next and saw some absolutely beautifully patterned baby girls' rompers. I felt the familIar pang of longing to have an excuse to buy them if I only had a daughter. Then I turned round and spotted exactly the same pattern on a baby boys shirt. I bought it. Who needs a daughter anyway?! 
