If you notice from the reviews, this product hasn't worked for a fair number of people who have tried it. I think I can explain why. There's generally four basic problems people have with their Achilles tendon:
-paratenonitis: this is where the covering of the Achilles tendon becomes irritated
-tendinosis: this where the actual tendon substance itself has a failed healing process going on because it's been overworked
-a partial tear: this is when you've torn the Achilles tendon partially
-a complete tear: this is where the Achilles is completely ripped apart
Out of the above four, one of the most common problems is Achilles tendinosis. This brace won't help with that problem, because the issue is that the tendon substance itself has a failed healing process going on - and slapping a brace around it does little to take the stress off the tendon to help it heal. This is because the tendon slides up and down, and this brace can't prevent that motion from happening. This good news, however, is that this problem can be fixed with certain exercises that can jump start the healing process (suggest checking out books like Treat Your Own Achilles Tendinitis
for more on that).
Now the other most common type of problem people have with their Achilles is paratenonitis - which is just an inflammation of the sheath around the actual Achilles tendon. That's a less severe problem, and for that, this brace can help. And this all explains why not al the reviewers here have been significantly helped by this brace, while others are completely cured.
It's really a good product for some Achilles problems, and if you're not sure what you've got, it's not a very expensive gamble to try!