Yep, I've got one. My main problem is with nerve pain in my back near the L4/L5 location. I also get sciatica (fire down the legs) and numbness, etc. The cord stimulator does help a lot with leg pains but it doesn't help much when my back is really hurting. So if you have mainly leg (sciatica) pain it will probably work well for you. As always though, you are not me and I am not you, so it could not work that well too.
Most surgeons and pain management docs will not implant one without a trial first, which is a good thing to make sure it works first. Be prepared to spend a few days with wires sticking out of your back for that.
Getting the location of the electrode correct is absolutely important for pain relief. They will likely install the electrode while you are conscious so that they can turn it on and get feedback about positioning and what you feel and where before they finalize the position. After it's locked down they can use the programmer to slightly tweak where the impulses are going - the electrodes have a lot of contacts with slightly different positions so that they can route the electrical signals to slightly different places after it's installed.
Spend the time to do as they recommend and get the program and selected electrodes tuned in by their rep. You'll want to do it once after the surgery and again after everything has healed up. After that every other year or so. This will keep it working as best as it can.