You should only be coming here for one of two reasons:
1) You live on CMU campus and/or have a CMU meal plan
2) It's 1:30 am and you are hungry (you are here because nowhere else is open nearby).
If you aren't a student or aren't craving food in the middle of the night, this place is not worth it. Do not go in expecting more than campus food quality.
That being said there are some items on the menu that are good. I like the skibo panini, PB Crunch sandwich (but only if you're on a meal plan because, let's be real, you can make this at home in 2 minutes), chicken artichoke and feta salad, the green peace-za pizza and the garlic chicken pizza. The froyo and sometimes the specials are alright too.
The biggest downside to the food here is that it's greasyyyyy. Except for the salad, everything you get is oozing with oil. Some things like the panini just look and taste greasy, other things like the pizza actually drip puddles of grease when you flip them over. This may hit the spot at 2 am when you have some drinks in your system but the vast majority of the time it'll make your stomach turn.
+1 to the staff being incredibly friendly. I used to come in often enough that they remembered who I was and sometimes even remembered what I liked to order. If I stayed there studying long enough I would even sometimes get a free hot chocolate or coffee! (though the coffee is pretty bad)
Know what you're getting when you eat on campus - if you set your expectations straight, you get exactly what you expect.