I had a chance to review the Shadyside restaurant Avenue B last year, and returned recently. Avenue B still offers excellent, inventive food with friendly, professional service. It's atmosphere is still casual (exposed brick walls, coarse paper over tablecloths on the tables, menu in chalk on the wall). Here's a link to my previous post.
The menu changes daily, with fresh and seasonal ingredients emphasized. While the dishes are typically no fussy, they do typically combine ingredients which look mismatched but which come together nicely. For instance, during my recent visit there was a foie gras appetizer offered with a quail's egg and maple syrup reduction. Other entrees which we encountered including a fresh sea bass with a saffron and vanilla cream sauce, and a flank steak with an excellent red wine demi glace.
The trick with Avenue B is that they are striving to offer an experience you won't see elsewhere -- crabcakes and grilled salmon are not the usual fare. Avenue B is well worth a look in Pittsburgh. Note that Avenue B is a BYOB, so if you'd like a glass of wine, bring your own bottle.