I have got two Airfryers, I bought a small cheap one first from Argos, mainly to use it as an Oven for our little Caravan. It works well, will do things like Potato Wedges, crisp up frozen Breaded foods, and can make a small cake with the 5inch diameter tin provided. It is However, far too small to provide a full meal for two using just one cycle, and some frozen items such as pies or fish fillets will not to in whole.
My new one is a 5ltr Model bought from Amazon, and it's far more practical to use than the smaller one, and could replace the main oven if needs be. Downside is it's bulkyness, it is fairly heavy to keep moving it around the kitchen, needs to sit on a heatproof mat to protect the worksurfaces, and sounds like a fan whilst switched on. The internal basket isn't dishwasher safe, as DH found out shortly after we bought it, some of the non-stop coating started to come off it, but thankfully we were given a replacement by the manufacturer as this fact was not made clear in the instruction booklet.