Let me preface this by saying that I am a native New Yorker who has been living in CA for 10 years.
I have been to Gio's multiple times with others and have always ordered a plain pie, New York size. The pizza is by far the closest I've gotten to true New York pizza while living in CA. Truly yummy by my standards and my non-New Yorker friends who have tried it have loved it.
I have to admit the atmosphere reminds me a bit of home. If you're expecting a fancy restaurant, you'll surely be disappointed. It's a no-frills pizza place with the focus where it should be--on the food! If you don't like the atmosphere, get your pie to-go. All pies are made to order, so expect to wait a little bit, especially for the larger pies. But there's a tv to watch while you wait if you don't have company to converse with.
Take Home Message:
For those of you who genuinely like pizza from places like Pizza Hut, Dominoes, Round Table, Little Cesar's, or are looking for "California" style pizza (like the stuff served at the restaurants with nice atmosphere's) or Chicago's deep crust pizza, you will all be very disappointed simply because this pizza is not what you are accustomed to. However, if you appreciate New York's pizza, you will not be disappointed! If Gio's was closer to where I lived I'd be eating here much more often. Instead I simply make sure I have leftovers to take home.