I have had both good and bad IPL experiences.
Initially I had the procedure performed by an experienced esthitician (on arms, back, shoulders and chest) and ended up with a very patchy end result, mostly on my back due to an ineffective machine. It got too hot, and caused a block like patchiness.
I seen the onsite dermatologist and expressed my dissatisfaction and ended up having a chemical treatment and several more IPL treatments (no charge) to correct the patchy pattern. It worked, and looked great!
Best advice, never just except the result if your unhappy. ALWAYS let the clinic know that you are unsatisfied with the result. The clinic recently purchased a new IPL machine and I've had two futher treatments done.
I LOVE the current results. I had very freckly arms due to extensive sunbathing as a child. My arms are practically freckle free, and no patchy marks. The treatments are worth it, if the issue your correcting bothers you that much.
Expect to experience dark sunburned like patches after treatment for a few weeks. You shouldn't have blistering or open wounds but it may be quite uncomfortable. Just be sure you go somewhere that is experienced, and has a physician on-site, not just on the sign on the door. Good Luck!