According to a recent study by the Brookings Institution, Pittsburgh is one of the 10 most "Walkable" Cities in America, ranking one spot ahead of New York. Good news, and something that I'm sure will be helped by the recent addition of the walking/biking path over the Hot Metal Bridge.
According to the study, of the 10 cities in the top 10, all but Seattle are served by some sort of Metropolitan rail systems. Also of the top 10, 5 of the 10 have "full" rail transit systems, and Pittsburgh is listed as having a "starter" syetem.
Give it a read, it's a great article on how good transport makes more livable cities, and good transport breeds new development. If you're interested, you could also check out the full study.
Still coming soon (seriously) - Pittsburgh City Line: Part 2