I'd give Pizzeria Libretto 3 stars because it is exactly A-OK.
The service is just fantastic - we were in the restaurant till late and they didn't rush us out and on the contrary made us feel welcome. They gave us wonderful recommendations and what was great were their plethora of vegetarian options.
The arancini were nice but the insides were slightly cold and it was quite garlicky. I also had the margherita pizza which was good but not memorable. I ended the meal with a cappuccino which was probably the highlight of the evening for me!
I think Pizzeria Libretto is the perfect place if you're going with a group or taking someone out you don't know well. The menu is easy and there is definitely something everyone would like and you know that the service will keep everyone in a good mood!