Better than people expect for a ship this far from a supply chain. Breakfast and lunch are buffet, and dinner is a la carte with options. Dietary requirements, including vegan and gluten free, are handled well, and it's worth flagging yours at booking rather than at the first meal. Some ships run a polar barbecue out on deck, which is exactly as good and as cold as it sounds.
Meals are included in your fare. Alcohol usually isn't, unless your specific fare includes it.
Timing bends around the day rather than the other way round. If a landing runs long or whales turn up, lunch waits. The galley is used to it.