Very cool area. I'm not originally from Pittsburgh, and when I came, I was shocked at the lack of a go-to "commerce/entertainment" district.
Well, market square is about the best Pittsburgh has to offer. It's not a big city, and most of this area (market square) really shuts down after 5pm, but it is somewhat lively on the weekends.
Much cleaner, and presumably safer, than South Side; although SS's bar scene/nightlife is much, much better.
It has a wide array of restaurants, both in choice of cuisine and prices. Not many shops around, and most are widely disbursed.
Overall, this area has soooooo much potential; but, in comparison with other cities, Pittsburgh's lack of a viable public transportation system really holds places like Market Square from being a premier entertainment destination.