I am 31 and I suffer from chronic pain due to Fibromyalgia and Sacroiliitis (the inflammation of a joint inside my pelvis). I have been using the INF 4160 for about a year and a half and love it, it is even more effective than a massage. It was given to me by my Sister in law (who is extremely happy with hers as well) and have been singing its praises since.
Over the years (since I was about 15) I have seen a number of chiropractors (who apparently made my condition worse, before we discovered what it was) and Physio's (who charge through the nose and usually only use their own version of this machine and a hot/cold pack on me). I do not have a driver’s licence so it is fantastic not to have to keep appointments half way across town.
I have 2 small children who need me to do a lot of bending over and picking up, it is really good to have something that i can just clip onto my clothing and keep doing what i need to without the pain, or after a hard day it is nice to sit and relax and buzz my pain away.
Also my Husband put his back out this week painting a ceiling, and was in excruciating pain until he decided to give my INF a try. He was able to go to work (as a mechanic) and work through it, coming home and putting the machine on again after work.  After 2 days he is almost 100% again.