In my (limited) experience, I've found them to be incredibly variable. I have one and it deals with oven-fry slop much quicker and with better outcomes than any actual oven I've used in my life. OTOH my partner's one takes at least twice as long for a worse result. So based on a sample size of two, you have a 50% chance of getting a good one.
Regarding air fryer recipes, it feels to me a bit like the consumer microwaves in the '80s. When they first gained widespread adoption here, there was suddenly an explosion of microwave cook books and stupid uni-tasking microwave gadgets like steamers, rice cookers and omelette makers (microwaving eggs is exactly as bad as you think, but we didn't know better at the time), all of which was only really designed to cash in on the trend. It wasn't for a good few years they settled into their niche of defrosting or reheating leftovers or frozen foods specifically designed for them.