For the most part the food is delicious. I have only ever ordered chicken burgers from them (and once a lamb burger) and they are usually very tasty and succulent, and the sides are similarly enjoyable. Importantly, they have a wide range of options for those of us with strict dietary requirements, and especially good are their gluten free offerings which we have never had any trouble with in terms of a reaction to. Unfortunately, it's not cheap to get the burgers gluten free, and if you are substituting ingredients for others ones (even just the sauce!) it will rack up extra frees. Also, they do tend to struggle with the sweet potato chips, which are often undercooked and/or under-salted. and the eggs are almost always overdone. I've found the snack chip portions are often skimped on, but the full size ones are generally fine.
Delivery orders generally take about an hour or less to arrive after placing, and I live approximately 10 minutes away by car, which I consider to be in good time.
That all being said, they have fairly frequently messed up orders, either wherein a burger has to be discarded because it's incorrect and doesn't meet dietary requirements, or just forgetting to add sides or drinks to the order. I don't really take issue so much with the mistakes themselves as from my understanding, Grill'd workers are underpaid and overworked, but rather the compensation offered for said mistakes. They will get back to you swiftly and politely if you submit feedback on it, but are reluctant to offer an actual refund, instead opting to mail you vouchers that one; are only for a free burger with the purchase of another burger, and two; can only be used in-store at Fairfield specifically within a meagre couple of months after the issue date. If I was able to visit the store myself, I would be doing that instead of getting delivery! This renders the idea of it being actually compensatory rather laughable.
Note: I have only ever ordered delivery from this restaurant, and have never been there in person. For this reason I am unable to comment on the service and cleanliness of the restaurant itself. Delivery orders I place are through the Grill'd website/app itself, not a third-party app.