We've used it twice for navicular. It does seem to have helped, at least a little. We have used the one time regional perfusions of Tildren, as that is less costly than the IV Tildren. Our horse also received navicular bursa injections of steroid, which do help him. I don't know if the Tildren helps him because his bones are not the greatest after 17 years of steroid injections. We've also used IRAP with decent improvement.
People seem to have varying experiences with it. It worked for one of my horses. It takes a while to see results so don't think it will magically make them trot off sound but I had really good luck with it. That particular horse is still sound and teaching kiddies the ropes in 2ft hunter classes. I do my own IV shots and chose to do the series of IV instead of the perfusion.
My vet, on the other hand, used it on his own horse that has navicular and it didn't do a thing. To be fair that horse has one of the worst cases I've ever seen and it was a last ditch sort of effort. He did a regional perfusion on his horse.
From what I've read the method of delivery (IV or a one time perfusion) has nothing to do with how well or if it works, though. I'm no expert though and haven't done much reading/research on it since I treated my own horse.