I only have 1 baby so can't compare surprise vs knowing but I do not regret having a surprise at all. I was convinced I was having a boy but turns out my instincts were wrong. Our baby was a long awaited ivf baby so we honestly didn't care about gender.
While lots of people prefer to know so they can buy gender specific things, I like that most of our stuff is gender neutral because if we do have a boy down the track, we don't have to go out and buy everything again.
I agree with a pp that the lead up to labour is exciting as you're at the point that you really can't wait to know if it's a boy or girl in there. We were given SO much pink stuff when she was born and I honestly think it would have been too pink crazy if people knew we were having a girl beforehand. I'd go a surprise again if we have another.