I've got a basic Philips
It takes on average between 1/2 and 2/3 of the time, and maybe a third of the electricity (assuming it cycles the same as a regular oven).
Quite impressed - convenient, and food tastes pretty good. It took me some getting used to, but basically anything that would go in an oven or under a grill. Oven chips a standout - the very cheapest (£1 for 1.5kg) come out very well IMO. Easy to keep clean - dishwasher safe. Easy to use - if I was to buy again I'd get the same basic mechanical timer type.
Downsides - it's another large thing to home, mine at least is quite noisy, and quite strong smells depending on what's cooking. I bought mine as an end of line at Lidl for £40 - they seem to be more than £100 - quite expensive for what they are.
Not sure about the health claims - mainly centre around fat, but I don't deep fry anyway so probably doesn't make much difference to me.