Air Fryers: Yes or No?

Both me and my gf are keen cooks but our friends keep telling us we need an air fryer (I would have thought it would have been something for us two to decide, but hey-ho). I've seen them in the shops and online but it looks like an extra bit of kitchen kit which we might not use that much anyway. If you have one, how much (in £s) did you pay and what sort of stuff do you do with it?