It is useful. But do not listen to all these clowns that knows nothing about cooking, telling you its the best thing ever.
The only thing that a air fryer can make arguably better or the same as your normal oven or stove is chicken pieces.
Air fryer is great for quick meals like all these little crumbed meat and veg things. It is also great for small meals if you are single or just 2 people. Or heating up some foods like pies and pizzas.
People and kids that does not know much about cooking, feel more comfortable with an air fryer. Our air fryer get used 90% by the kids,
I have this one (8L) and it is one of the biggest you will find. Works great, are cheap and you can fit proper size chickens etc in it. Think I have it for more than a year and it still works perfect, no rust, like some brands we shall not mention.
www.pnphome.co.za