The vast majority of people are very happy with the results. But while it is generally very safe, there are risks, and if you are one of the unlucky ones to experience the adverse consequences, then you may very well regret it. Worst case scenario is very bad.
From WebMD: Lasik Risk and Rewards provides a pretty balanced view:
https://www.webmd.com/eye-health/news/2 ... -the-risks
For a more negative view, there is a site called lasik complications.
PRK may be considered slightly lower risk than LASIK, because there is no "flap" created. But PRK has longer recovery time.