I absolutely know why they call this the best ballpark in the US. I may be biased because I'm from Pittsburgh, but this place it amazing! I've been there multiple times over the years and I have yet to find an awful seat. The views of the city are breathtaking. Definitely a must for your out of town guests! It was even fun to go when the Pirates weren't doing so great!
My main tip is to catch a game on Fireworks night. They are the best fireworks I've witnessed in my life (and I've been to Disney). With Pittsburgh as the backdrop and the fireworks glimmering off the reflection of the buildings, it doesn't get much better than that!
Tickets are reasonably priced, also the "All You Can Eat Seats" are fun! Drinks are DEFINITELY expensive, so I would recommended pre-gaming before the game at Mullens. Which is right across the street, at the end of the Roberto Clemente bridge.