It's convenient but it's not great.
positive: speedy, better than other fast food options when you're in the area
negative: food is only so-so, extra charge for guacamole
I had the cilantro lime shrimp burrito. The shrimp, while nicely sized, didn't really taste like either cilantro or lime. The whole thing became a bit of a soggy mess at the bottom, particularly when I was fighting to peel the grilled tortilla from the aluminium foil...
I really liked tamarind variety of Jarritos (Mexican pop) in the cooler!