Yes I had one session then a day after a couple of coincidental things happened.
I was about to switch a light on and suddenly thought "I hope the bulb doesn't blow" and as I switched it on, the bulb blew. The following day I suddenly thought "I wonder when that courier is coming to collect my parcel" at that very moment the doorbell rang and it was the Courier. I'd been waiting over a week for an unwanted item to be collected.
They do say Reiki can open the Third Eye Chakra, so who knows. As for pain relief, I saw no difference but then only had one session.