I think there are so many different opinions, simply because there are so many devices that describe themselves as air-fryers that do the job to varying degrees of good or bad.
I had been looking at them for a while - mainly the Tefal Acti-Fry - but was put off by the small amount they seemed to cook for the large top-space they took up. Also the price, which I'd be happy to pay, but only if I knew I would use it.
So I gave up on the idea, until this year, during Black Friday, where I picked up a Blusmart Power AirFry from Amazon. A brand I hadn't heard of, but the price was right (half of anything I had seen) and the capacity seemed decent (3.2 litres). I looked at the reviews and decided to chance it.
My Air Fryer sits upright, so takes up less top space than many. It certainly isn't rocket science - it is simply a very small fan oven. However, it does do the job brilliantly. I've been cooking chips (fries to you you guys), battered fish (frozen), pies, etc. I even found that a cake tin I had fitted with an inch all round, and successfully cooked chocolate brownies in it.
There is nothing I have cooked in it that I couldn't cook in my oven. But because I am often cooking for one, it makes more sense than heating up the whole oven for just a piece of fish and portion of chips.
And - unlike other folks experiences here - it is quick. The instructions recommend you turn it on empty for 3 minutes before putting food in it. But once heated up, I can do a piece of fish, fries and onion rings for one (all from frozen) in about 12-14 minutes. I don't think that is unreasonable. The chips are nice and crispy on the outside, while soft inside. The fish is exactly as I would expect it out of an oven - not like traditional deep-fried fish in batter, but quite acceptable as a quick meal grabbed out of the freezer.