I picked up a Ninja Foodi toaster oven style air fryer a few weeks ago. I do have to say I'm pretty impressed with it. Is it a life changing cooking device, no. Is it handy, yes.
First of all, air fryers are really just small convection ovens. So, if you already have a convection oven, you probably won't be overly impressed with one. I opted for the Ninja because it will toast bread and fit more food that several of the coffee pot/deep fryer shaped units. Just like cooking appliance, you have to learn how to use it. It's not complicated, but when using the air fry mode, you have to adjust temperatures on frozen foods with conventional oven directions. Usually like 25 degrees lower and 20 percent less time.
Today for lunch, we made some excellent 'fried' potatoes. Cubed up a few yukon golds, sprayed with canola oil, sprinkled with Oakridge SPOGOS seasoning, tossed around a bit and put in the air fryer for 24 minutes at 400 degrees, pausing and stirring/tossing half way through. Came out pretty darn good, nicely browned just like the cast iron fried potatoes my grandma always made. Very similar to Perkins breakfast potatoes, but better seasoned. We've made standard Ore Ida steak fries several times. 400 for 18 minutes. As good as what you get at Red Robin by time they usually get to your table. We've also tried Toasted Ravioli, Onion Rings, other frozen fries, etc. Still learning the instruction adjustments on some of the non-potato items, but have turned out pretty good. I just know I can get them a little better. My favorite air fryer indulgence though...Pizza rolls. 6 minutes @ 400. Make the total time from power on to on your plate like 7-8 minutes as it preheats in just a minute or two. Best pizza rolls I've ever made.
It also bakes pretty well too. We've cooked a couple frozen pizzas and my wife made her light bagels in there this morning. She said it baked better than our regular oven. So, for this model, it makes a nice little quick pre-heating oven for smaller baking needs as well as a nice second oven when you have things that need to cook at different temps.
My take on it is, if you crave unhealthy fried foods, it's a way to make very similar tasting stuff at home that should be quite a bit healthier for you than from a deep fryer.