Arriba is alright. I haven't been to any other location, so I can't compare between Ahwatukee and elsewhere; but this location is adequate.
The Good:
They actually have a pretty decent breakfast on the weekends; and you get a side of pancakes with breakfast too! The Queso dip is a tasty appetizer (it has chorrizo in it, mmm!). And the $.99 Happy Hour Margaritas are reason enough to visit Arriba.
The Not-So-Good:
The service is pretty spotty. Sometimes you're waiting a while and the restaurant isn't even crowded. And I wouldn't say they're the friendliest group of people either -- not rude, but not friendly. The food is sort of uneven as well: some winners and some duds. And pay attention to the heat levels on the menu; some of the dishes are HOT.
Overall, Arriba is a decent middle-of-the-road Mexican dining option. I'll undoubtedly be back...for sure during Happy Hour.