I've been to Zizzi quite a few times, and have to say that every time the food has been of a good standard, large portions and the service excellent. Overall good value for money.
To respond to some of the other reviews (and no, I do not work for Zizzi or have any other connection other than as a customer): Laura K - the food I've had has always been tasty (maybe it was just the dish you ordered that was "bland") and your complaint about the Tastecard not saving you much money is more a complaint about Tastecard, not the restaurant, so unfair to use in your rating for the restaurant. K12ST - Saturday's aren't always quiet at Zizzi's - but at least because it was you were able to get a table, rather than having to wait!
I definitely recommend Zizzi to those looking for a good meal in Stortford.