I have three ds, no daughter to compare to - no sister for me either! I definitely longed for boys, although I found that many people found this difficult to accept - lots of "but SURELY you want a girl this time?"
Someone said earlier that they were fearful of being a role model to a daughter, I would agree - my mum was very hard on me compared to my brother, her expectations were so hard to live up to.
But then you can trace a lot back to her experiences, too. Youngest of four girls, her parents devastated by never having a son - I think she felt determined to "prove" through me that girls could do whatever they wanted. Or in her case, what she wanted for me!
My MIL was devastated by the birth of each of my boys - she constantly harps on about what a disappointment it was to have boys, which is sad for my DH and his boys. But then again - she was the youngest of five girls before the much longed for only boy arrived, so I can see how that happened. Apparently, her own father blamed her mother for the lack of a son and said that "at last" she'd done what she was bloody well meant to do when the boy was born.
Just be aware - you reap what you sow in terms of the messages you send your dcs, and sometimes making up for the prejudices you experienced could have unforeseen consequences!