I did not find out with any of my boys, I don't really know why, I just think that you aren't meant to know before the birth.
I absolutely loved the idea of just being the Mum to a little 'being' and then after all the (damn) hard work of labour, having that amazing surprise at the end of it.
I didn't decorate a nursery, all my boys co-slept, and I'm not interested in gender specific clothes for babies, so it was no big deal for me.
I also had no ultrasounds with my 3rd child, so there was no chance to find out, even if I'd wanted to.
I'd do it the same if I were ever pregnant again.