I also agree that that's all it does, because I reinjured less than 3 weeks later while wearing supportive shoes, inserts and walking on a flat dry smooth pavement.
I have to say that it was extremely painful before the shot, and even after the reinjury it was not as bad as it had been, the cortizone got in there and broke up the inflammation which I believe allowed the foot to begin to heal itself (I probably could have done the same thing with a mega-dose of Daypro).
I will never have another cortizone shot, but it did temporarily remove the pain as a last ditch effort to get the tendon to settle down. As long as you think of it that way, and not as a cure itself, and as one-time only, I'm ok with that. My problem is when the shots are given multiple times and/or touted to the patient as a cure.
Stay well and let us know how you're doing, we care, and we can also use some good news. I suspect a lot of healed people don't come to the board anymore, so we have a skewed sample overrepresenting the bad outcomes.