I have used it twice now.
One case - Mia - is doing amazingly well! She was diagnosed around the middle of Dec 2012. She was given bromo but it took a bit for it to start working. I had to supplement with dex, every other day, for about 3-4 days. Once she was stable, I stopped the dex and for over a month she was fine. 2 weeks ago I had to start supplementing with Dex again, but she gets a boost every 3-4 days instead of the every other day. She still looks great! Nice thick coat, can eat well, still runs normally (lol well as normal as an old rat can run, her HED makes her running look a bit funny). All in all a pretty good response.
The other is my silly Lily and honestly, I don't know how much the bromo is actually doing. She had been getting both dex and bromo because it was a very unusual presentation for a PT and we weren't sure. Since the side effects are relatively minor in comparison to what she was experiencing, we put her on it. When she plateaued, I stopped all of her meds except for dex which requires the rat to be weaned off (she was on a tonne of antibiotics for respiratory and such - total of 6 meds). I almost lost her when she was off the meds so we started her up again on bromo and dex, I think the combo of the 2 are helping. I also think that the bromo was doing something since when I stopped the bromo but not the dex and she regressed pretty badly. She seems "ok" this morning... But its difficult to say with her, she is a very unusual case.
Its definitely worth a shot if a rat has a PT. Just a word of advice, when going to get the drug from your vet ask for a script and go to the human pharmacy if the vet will give you one. It is much much cheaper there (usually).