Trams is, IMO, the best Vietnamese restaurant in Pittsburgh. Although their menu isn't huge and they don't offer my favorite noodle soup, bun bo hue, everything that I've tried is super yummy! Plus, they have good prices!
I always start out with fresh spring rolls. I think they could use a little bit more fresh herbs in there, but their dipping sauce is really good. I'm also a huge fan of the mixed/special vermicelli noodles. It comes with tons of grilled and shredded pork, a crispy spring roll, and veggies on the bottom. Always enough for two meals too.
Service is always very quick as well, and the owner is really friendly!