I wouldn't say it hurts, ocassionally on the thicker hairs you will get a sensation of a small Elastic band being pinged on the skin.
The part I found most uncomfortable was the cooling air system which works in conjunction with the Laser zaps. The cooling air is quite cold and I found it took my breath away. I had a good Technician though who told me when she was going to do a Laser pass, I could then take a deep breath in and hold it for a few seconds which really helped. Also she used a wooden spatula to block off the Nostril she was working closest to. The treatment is quick though, I had chin and above my upper lip done and each treatment lasted no longer than 5 minutes.
The important thing when you have Laser hair removal is to keep out of direct sunlight and wear a good high factor sun block. I would definitely recommend the treatment, as would my friend who recommended me to the clinic. She suffered from unsightly facial hair since her teens and she also thinks the treatment is a Godsend.