As with anything in the entire world, it works for some and for some it does nothing.
I had my dogs on the level 5000 (liquid health) and for a time, several years, it did seem to help them all.
Eventually it didn't seem to do much for my oldest dogs, so I tried rimadyl and the difference was amazing. So the younger dogs get the liquid health and when it is no longer helping them, they go to rimadyl. My 14 year old would be gone without her rimadyl, no question in my mind at all. But I think that the liquid health did let her get to the old age of 13 before we had to do something stronger or different.
I have tried Springtimes stuff for humans with not one iota of effect on my sore joints. I tried a different brand of glucosamine/chondroitin/msm and nothing at all except my money dissapearing. I take advil and get relief, it works and I'm not going to argue with it.
As with anything, try it, it might be just what the doctor ordered or it may do nothing at all for you or your pet.