I'm an all or nothing girl I think - either no one knows, including the mum&dad, or everyone who wants to know can know.
I think that the anticipation is good either way, regardless of whether you're waiting to find out, or waiting for the arrival of your son or daughter. The main advantage i see with telling is that you get gender specific clothes, and you can decorate your nursery in advance without having to worry about hiding the clues if you know what you're having but haven't told.

The people who treat it like a power thing are just weird IMHO - who gloats about people guessing wrong like that, that's just a bit pathetic. Maybe I'm just too out-of-touch with these things, but I've always thought a healthy arrival is more important than the flavour.

Good luck though, whatever you choose it's a very exciting time.