I always thought this was an appliance I just didn't need, but my kitchen is in the center of my house where air doesn't circulate particularly well, and I got tired of all the lingering smoke and odors when cooking some items on the stovetop, especially meats. So after carefully reviewing the great selection of recipes and ideas from our friend the Blue Jean Chef, Meredith Laurence, I finally bought one last month.
The first thing I air fried was steak, and it came out juicy and wonderful with a little bit of a crust on the outside, just as we'd hoped—but best of all, as soon as the cook time was over and we washed out the basket, there were no lingering odors at all! I was very happy and started air frying all kinds of things, and everything had great results. Like a few others here, we don't eat many of the foods you may traditionally associate with an air fryer, but it has been fantastic for quick and easy cooking/baking of lots of different foods in a shorter time and without heating up the whole kitchen.
From my research, I can tell you that most air fryers nowadays are pretty good. The three things I'd note are:
Check the basket/drawer dimensions carefully to get an idea of how much food will fit in it; regardless of any capacity given in a description for quart size or anything else, that will be a helpful guide to determine which air fryer to buy based on how many you're feeding and what you plan to cook. (The link shared above to the Blue Jean Chef's recently posted buying guide is great as well.)
Spend the (usually minimal) extra money to get a digital model. My only regret with the air fryer I purchased is that I decided to go with the cheaper dial model, and I worry that it won't hold up for a long time because the dials are essentially like old-school kitchen timers where it feels like they might break if you move them back and forth. You don't necessarily have to get a fancy touchscreen version, but the models with buttons seem far more sturdy and reliable.
Definitely go to bluejeanchef.com for lots of usage and recipe ideas. Meredith has done a great job of helping new air fryer users get to know their machines and find delicious things to make in them. Her air fryer books are also excellent and are available in print or on Kindle.
Good luck, and happy air frying! 