I find Sbarro's slices not awful, which is more than I can say for some other chains. That said, they're decidedly unremarkable, and a bit pricey for what you get.
I think they've survived on 'being there'. A pizza option in the food court. But if 'being there is half the battle', then it looks like that part of the battle is getting more difficult.
A mall near me recently opened a food court featuring Chipotle, Elevation Burger, Freshii, ban, and more to come. I don't think a Sbarro will ever fit in.
Time to compete guys.