I don't have experience with those or have heard of them honestly, but I would assume the success in them is entirely up to how much your current weight is and what your expectations are. Sounds like a good option if you've already dieted and exercised to your ideal weight and have a stubborn fat spot that won't go away with exercise.
I have a "muffin top" type thing going on which I hate, and although it's shrinking, it's still there and doesn't seem like it's going away for awhile. If it's still a trouble spot for me after reaching my goal weight, I may consider a treatment like this to get rid of it, but for now, I'm planning to wait it out and hope it goes away on its own as I continue to lose weight.
Best of luck to you!