Well, I just was wondering because people seem to have some strong opinions either way. I am especially interested in hearing if you have actually used it.
I have personally become a fan. Here's why...
Gareth was suffering from an unknown something or other, and it really wasn't looking good. He had a giant red spot that appeared on his side, and a few days later, his scales started sticking up. I was prepared for the worst. Anyway, I went to the local pet store (I live in the middle of nowhere, and as much as I wanted to save Gareth, I wasn't paying $30 for overnight shipping on meds that may or may not have done anything) but the only thing they had that wasn't for fungal infections was Bettafix, so I got it, figuring it at least couldn't make things worse, even if I was relatively sure it wouldn't do anything (mostly for fin rot and such).
The next morning, the red spot was completely gone. The day after that, he started to perk up, swimming all over the tank. Then, his scales were no longer sticking out and his bloating went away, and he started lifting his gill covers, as if trying to flare. The day after that, he actually ate something and gave me a small flare (he never did really do a full flare, he's always been really passive). Now, he's back to his normal self.