Pizzeria Due--and for that matter, Pizzeria Uno--is a hallowed member of Chicago's All Star Places To Get A Pizza. I had the chance to go there recently with some distinguished company and all involved were impressed. The pizza is very well made, there are lots of varieties, the price is reasonable, the service is friendly and swift and the environs are clean and welcoming. It is less difficult to get a seat at Due than it was at Uno's (in large part because Due had a more extensive number of available tables but also because Uno is tremendously popular), but both restaurants do a clever thing by getting orders from their customers at the moment that they arrive and put their names on the waiting lists for tables. Of course, this means that either one's entire party has to be there, or that at least one person must know what the group wants to eat. While you wait, Due has a bar with which one can become acquainted in friendly fashion, and the drink selection is significant.
I recommend trying some form of deep dish pizza at either restaurant when going there. Life is too short to be without Chicago deep dish, and when you eat at either Uno's or Due's, you will swiftly and certainly understand why Chicago is so renowned for its pizza fare--and why we Chicagoans are so spoiled when it comes to pizza.