Slices is the kind of place that people go to for lunch because it's close. Don't get me wrong, it's not bad. But the quality of the food is really secondary to the location. If you like people-watching, you can stare at the freaks on Mill Ave while you nibble on some pizza. It's also near to ASU, so if you're stuck on campus without a car, this is a good option.
The food itself is pretty average. Slices has some really creative pizza ideas- pesto with feta cheese, loaded baked potato, and enchilada are some of the more odd varieties. Unfortunately, their creativity is hampered by their practice of pre-making all the pizza.
The pizza is always ready-made. Slices seems to use the same sort of half-prepared method that Sbarro in your mall's food court used to. They cook it almost to the point of being hot and then let it sit until someone orders a slice. Then, the slice goes into the oven so that it's oven-fresh temperature if not oven-fresh tasting when you get it.
This place gets busy and seating is limited, so avoid busy hours if you're unwilling/unable to stand or find seating elsewhere.