I've had a few very expensive IPL removers that I was sent to trial over the years.
They don't work on dark skins, on areas of uneven pigmentation, on grey, red or blonde facial/body hair and can't be used on irritated/sensitive skin.
I've had some success with underarm hair and on my bikini line but it does grow back. You can only use the IPL on stubble as the hair root needs to be present to be zapped.
I stopped using the IPL's on my face, as I was concerned that my hairs weren't dark enough. I was also sent a facial epilator with a very narrow head that works a treat. It has a forward and reverse action to pluck hair growing in both directions.
When I had my eyebrows threaded I was astonished at how painful I found it, compared with epilating my upper lip, bikini area and armpits myself with various machines.
I thought I had a high pain threshold but threading my eyebrows gave me a rethink. I was sat in a chair in a shopping centre mall so couldn't exactly show any reaction, either!
The facial epilation sensation to me is a sharp prickle but deals with a lot of hairs at once. In the right light you can see the hairs flying in to the air as they are plucked. I think regrowth has been weaker following repeated plucking sessions, despite the old wives tale that it encourages growth.