I had one for quite awhile, it pretty much killed any sort of release i had developed over the years (what a mistake that was). In the end i took it off and found my accuracy actually increased, the downside being my wrist was pretty weak and my release was up the creek. Took me a good 2-3 years to repair the damage one of those things had done, you could see it was an issue when i started making huge improvements each year once i got rid of the thing.
Im like the others here, i dont advise you use them unless you need to. If you have a weak wrist (due to injury or otherwise) and need the support, then they can aide your game. For pretty much anyone else i feel they do more harm than good.