I did at first, and was really excited about the 20wk scan to find out. But then I started harbouring worries that maybe I wanted more than the other, that just upset me. DH had made intermittent noises about maybe not finding out, we had a long chat about it and I realised that all of my worries were mostly based around not bonding with it - pregnancy seems so abstract still, I thought knowing the sex would make me feel closer to it.
Now I just actually don't care, and am far more involved in buying it things that steer vastly away from anything to do with so-called gender things like I started a little library of children's classics to read to it, started a video project of filming our lives while it's still a bump, and begun thinking about it more as a person than a particular sex.
I dunno - none of this is to cast aspersions on what anyone else does. Just for me personally, I had my worries and we came to a decision that put those worries to bed.