I've been on Tysabri for the last 2 years and am coming off it in Janurary. It has been a great drug for me, I had no relapses while on it and had increased energy and decreased symptoms. The risk of PML goes up the longer you are on it, and I lost my health coverage for it, otherwise I'd love to stay on it forever!
I'm happy to answer any questions you have.
Diagnosed with MS April 2006
Started Tysabri Nov. 2007