Appt came through for 20 week scan. We're undecided if we should find out the sex or not. I did for DD and was glad I did, I wanted a girl and was thrilled to find out I was getting one 
I really have no preference this time. DD wants to find out...DP doesn't know whether we should or not...I'm not sure....
What do you think? Did you find out? Are there any reasons we shouldn't?