Speaking as someone with lower back pain who has actually undergone spinal decompression therapy (off and on for the past 2.5-3 years or so, in fact), I found it to be the only effective treatment to deal with my pain issues. I suffered from fairly constant low-level pain that would spike if I overdid something because I thought there wasn't anything I could do to mitigate the issue; physical therapy didn't do much, if anything. I started to see my chiropractor at the recommendation of a physical trainer I was working with at the gym, and I don't regret it for a single instant. Spinal decompression, if done correctly, does work; the trick is to find a doctor who isn't using it in drastic fashions. My chiro actually pioneered the protocols for the treatment in the area I'm in currently, such as placing an upper limit on the "pull" the machine does (he doesn't go above 75 pounds of pull; some people were arguing that it could go up to half your body weight, so in a 200 pound person, that's 100 pounds of pull!). My recommendation, if you do decide to go through with it, carefully ask the doctor about the protocols he/she follows, ask if you can observe how the machine actually works, and ask what else the chiro will do to help ease the pain. My doctor combines electrostimulation with some deep tissue work and the spinal decompression; he rarely adjusts me, and then only when it's fairly clear something's out of alignment.
Long and the short of my response; be careful, ask questions, but don't brush off a potential pain-relieving therapy. It really does depend on the how the chiropractor implements the therapy, in my opinion, as to whether it works or not.
