Question
For those that automatically dismiss IPL as a "fake" laser, etc, this excerpt was taken from an actual medical study:
The use of light and laser for hair removal has evolved during the past few years. Laser systems such as the ruby laser (694 nm), alexandrite laser (755 nm), diode laser (810 nm) and neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (1,064 nm) are commonly used in hair removal. However, permanent hair removal has been difficult to achieve using lasers owing to the long growth/rest cycle of normal human hair follicles. There is still an increasing demand for safer and more efficient hair removal techniques. The latest and most effective choice in the treatment of hair removal is non-coherent intense pulsed light (IPL), which is both efficient and safe for hair removal. A group of 210 patients with skin type III-V were treated for superfluous hair in different areas of the body (face, extremities, axillae, bikini line and back) for three to five sessions at 6-week intervals using IPL. There was a significant hair reduction of about 80% with no side effects and minimal complications. Follow-up was done 6 months after the last session. In conclusion, IPL is very effective and safe for hair removal.

Answer
For those that automatically dismiss IPL as a "fake" laser, etc, this excerpt was taken from an actual medical study:
The use of light and laser for hair removal has evolved during the past few years. Laser systems such as the ruby laser (694 nm), alexandrite laser (755 nm), diode laser (810 nm) and neodymium:yttrium-aluminium-garnet (Nd:YAG) laser (1,064 nm) are commonly used in hair removal. However, permanent hair removal has been difficult to achieve using lasers owing to the long growth/rest cycle of normal human hair follicles. There is still an increasing demand for safer and more efficient hair removal techniques. The latest and most effective choice in the treatment of hair removal is non-coherent intense pulsed light (IPL), which is both efficient and safe for hair removal. A group of 210 patients with skin type III-V were treated for superfluous hair in different areas of the body (face, extremities, axillae, bikini line and back) for three to five sessions at 6-week intervals using IPL. There was a significant hair reduction of about 80% with no side effects and minimal complications. Follow-up was done 6 months after the last session. In conclusion, IPL is very effective and safe for hair removal.

Answer
the problem is not with the IPL, it's with the techs who operate them. These machines are meant to do various skin procedures and that's what most of the clinics get it for. Then, unexperienced uninformed techs at those clinics end up performing the procedure without knowing much about hair removal, which usually results in either lack of results or burns. Most clinics that are focused on hair removal specifically purchase the more expensive machines that are real lasers.