I have the original tria IPL and it works extremely well. After 3 sessions easily 80% reduction as long as you use it a 4/5 or 5/5 power. Go slow and let the glass plate cool as it quickly gets very hot. Anything less and it won't kill put sufficient heat at the root to kill it. At 5/5 the 1st time at a new hair follicle you can feel the heat go down the shaft and explode the root... Yes it hurts, especially on a old thick shaft. Each time there after the pain is minimal to non painful after the 2nd to 3rd time,
I have come across a hair regrowth study where it shows if you more then5 hairs in a small area like 1cm squared or something like that, it can actual cause dormant hairs to grow again. So people who laser or IPL need to understand that is why it takes a while because as you kill some you unavoidably cause new ones to grow... But the net result is almost always a reduction so it doesn't matter that you trigger new hairs to go, as long as you keep on it and with 6months you'll be hairless and with a few very fine hairs.