Steelers fans love it, well mostly because they are Steelers fans. Therefore, when they review Heinz Field most of them in a way are reviewing the Steelers. Sure they are going to give 5 stars to where their favorite team plays.
I'm not a Steelers fan so I will try to be objective. I've been to a number of pro and college stadiums and Heinz Field field is just OK, thus the 3 stars.
It's way too open, and though Steelers fans get very loud, it doesn't get close to as loud as old Three Rivers used to be. The turf is bad. I love how they want to keep the real grass, but when the Steelers, the Panthers, and the entire WPIAL championships are played there the grass just can't hold up and it turns into a mud bowl. Its really time to lay the fancy new synthetic field turf like many of the other stadiums.
And for a college football venue, it really sucks. Terrible college atmosphere mostly because its 3 miles from campus and all the students have to bus in. But in order to have a beautiful basketball stadium Pitt had to get rid of old Pitt Stadium and play their games at Heinz, so I understand PITT's decision to play here.