I've been to a couple, pre and post baby.
If you print off the free ticket then it's not too bad to go and have a look around. Most of the products there are superfluous and unnecesaary (and overpriced for the show so they can ''offer' a great deal).
I found it great to be able to touch and feel cloth nappies before I bought them as there aren't many places in Sydney you can do that.
If you know what you do and don't need and approx prices on everything and won't be sucked into a bad deal, then it's good. There used to be free samples of everything, but now not so many and not so great samples.
lol there are also a LOT of those nasty pram mothers there too - I used to feel like saying "hey we're all here for the same purpose love!"