I think this is pretty much my favorite airport in the country. I used to fly in and out of this airport when I was a kid. It was pretty bad. In 1992, PIT transformed the airport from an arrangement of what we called 'pig troughs' to one of the nicest airports in the country. It is open, airy and it has art exhibits scattered around the terminals.
Megan Herwig: The Block Clouds: Mixed Media
PIT was the first airport in the country to use the AirMall concept. This is different than other airport marketplaces because the prices are not inflated to airport pricing; they are priced as any other mall in the area. It's meant to feel like a local mall and it has enough shops to fill a galleria. PIT has also received top status in Condé Nast Traveler’s '2009 Business Travel Award' for the areas of shopping, dining and amenities.
[calder mobile exhibit via flickr]
There is one common terminal for all arrivals and departures. The terminals have a spacious layout that feels 'uncrowded'. There are plenty of restrooms and there are help-desks for visitors on the airside and the landside.
A feature that I particularly like is that they provide all postal services including USPS, FedEx and UPS. They even have a RiteAid.
If you get stuck there for some reason, there is a Hyatt Regency attached to the airport. You don't even have to go outside. (You will have to go through security to get back in, though.)