I tried it once but couldn't remember to take the pills everyday. I lasted maybe 3-4 weeks and didn't notice a difference. I've heard it takes a while to take affect though. Some people swear by it.
I don't take it, but my dog is getting a little arthritic and had started limping around, especially after he would run a lot. I started him on chondroitin and glucosamine and he has pretty much stopped limping. It couldn't hurt to try.
there is nothing dramatic about the effect, its suttle - pain should subside, however joint health should improve over the long term. The MSM will make your hair grow like crazy, this is known also, so be prepared to shave more often.